S-3

As filed with the Securities and Exchange Commission on October 15, 2003

Registration Statement No. 333-          

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SONTRA MEDICAL CORPORATION

(Exact Name of Registrant as Specified in Its Charter)

Minnesota	41-1649949
(State or Other Jurisdiction of Incorporation or Organization)	(I.R.S. Employer Identification No.)

10 Forge Parkway

Franklin, Massachusetts 02038

(508) 553-8850

(Address, Including Zip Code, and Telephone Number, Including Area Code,

of Registrant’s Principal Executive Offices)

SEAN F. MORAN

Chief Financial Officer

Sontra Medical Corporation

10 Forge Parkway

Franklin, Massachusetts 02038

(508) 553-8850

(Name, Address, Including Zip Code, and Telephone Number,

Including Area Code, of Agent For Service)

Copies to:

KEVIN P. LANOUETTE, ESQ.

Browne Rosedale & Lanouette LLP

31 St. James Avenue, Suite 830

Boston, Massachusetts 02116

Phone: (617) 399-6931

Fax: (617) 399-6930

Approximate date of commencement of proposed sale to public:    As soon as possible after the Registration Statement becomes effective.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ¨

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  x

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box.  ¨

CALCULATION OF REGISTRATION FEE

Title of Shares to be Registered	Amount to be Registered		Proposed Maximum Offering Price Per Share(1)		Proposed Maximum Aggregate Offering Price(1)		Amount of Registration Fee
Common Stock, $0.01 par value per share (the “Common Stock”)	15,360,000	(2)	$	2.795	$	42,931,200	$	3,473.14

(1) Estimated solely for the purpose of calculating the registration fee, and based on the average of the high and low prices of the Common Stock on the Nasdaq SmallCap Market on October 10, 2003 in accordance with Rules 457(c) under the Securities Act of 1933.

(2) The Registrant has completed a private placement to selected qualified purchasers of units consisting of shares of the Registrant’s Series A Convertible Preferred Stock and Warrants to purchase shares of the Registrant’s Common Stock (the “Private Placement”). The Registrant is registering for resale (i) 7,000,000 shares of Common Stock issuable upon conversion of shares of the Series A Convertible Preferred Stock, (ii) 560,000 shares of Common Stock, representing the Registrant’s estimate of the maximum number of shares of Common Stock issuable upon conversion of accrued dividends on the shares of Series A Convertible Preferred Stock, (iii) 7,000,000 shares of Common Stock issuable upon exercise of the Common Stock Purchase Warrants issued to the purchasers in the Private Placement, and (iv) 800,000 shares of Common Stock issuable upon the exercise of the Common Stock Purchase Warrants issued to the placement agent in the Private Placement. Pursuant to Rule 416 under the Securities Act, the shares being registered hereunder include such indeterminate number of shares of Common Stock as may be issuable with respect to the shares being registered hereunder as a result of stock splits, stock dividends or similar transactions affecting the shares to be offered by the selling shareholders.

The Registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until the registration statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information in this prospectus is not complete and may be changed. The selling shareholders named in this prospectus may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and the selling shareholders named in this prospectus are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED OCTOBER    , 2003

PROSPECTUS

SONTRA MEDICAL CORPORATION

15,360,000 SHARES OF COMMON STOCK, $.01 PAR VALUE PER SHARE

Sontra Medical Corporation has completed a private placement to selected qualified purchasers of units consisting of shares of our Series A Convertible Preferred Stock and Warrants to purchase shares of our Common Stock (the “Private Placement”). This prospectus relates to resales from time to time of:

• 7,560,000 shares of our Common Stock issuable upon conversion of the shares of Series A Preferred Stock issued to the purchasers in the Private Placement, including our estimate of the maximum number of shares issuable as a result of the conversion of accrued dividends on the shares of Series A Preferred Stock;

• 7,000,000 shares of our Common Stock issuable upon exercise of the Common Stock Purchase Warrants issued to the purchasers in the Private Placement; and

• 800,000 shares of our Common Stock issuable upon exercise of the Common Stock Purchase Warrants issued to the placement agent in the Private Placement.

All of the shares being offered by this prospectus are being offered by the selling shareholders named in this prospectus. This offering is not being underwritten. We will not receive any proceeds from the sale of the shares of our Common Stock in this offering. Upon any exercise of the warrants by payment of cash, however, we will receive the exercise price of the warrants, which is $1.50 per share for the warrants issued to the purchasers in the Private Placement and $1.20 per share for the warrants issued to the placement agent in the Private Placement. The selling shareholders identified in this prospectus, or their pledgees, donees, transferees or other successors-in-interest, may offer the shares of Common Stock or interests therein from time to time through public or private transactions at prevailing market prices, at prices related to prevailing market prices or at privately negotiated prices.

Our Common Stock is traded on the Nasdaq SmallCap Market under the symbol “SONTC.” On October 14, 2003, the closing sale price of our Common Stock on the Nasdaq SmallCap Market was $2.85 per share. You are urged to obtain current market quotations for the Common Stock.

Investing in our Common Stock involves a high degree of risk. See “ Risk Factors” beginning on page 9.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is         , 2003.

TABLE OF CONTENTS

	PAGE
Where You Can Find More Information	3
Incorporation of Certain Documents by Reference	3
Prospectus Summary	5
Risk Factors	9
Special Note Regarding Forward-Looking Information	17
Use of Proceeds	18
Selling Shareholders	18
Plan of Distribution	22
Legal Matters	23
Experts	23
Indemnification of Directors and Officers	24

No person has been authorized to give any information or to make any representations other than those contained in this prospectus in connection with the offering made hereby, and if given or made, such information or representations must not be relied upon as having been authorized by Sontra Medical Corporation, any selling shareholder or by any other person. Neither the delivery of this prospectus nor any sale made hereunder shall, under any circumstances, create any implication that information herein is correct as of any time subsequent to the date hereof. This prospectus does not constitute an offer to sell or a solicitation of an offer to buy any security other than the securities covered by this prospectus, nor does it constitute an offer to or solicitation of any person in any jurisdiction in which such offer or solicitation may not lawfully be made.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and other reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy any document we file at the Securities and Exchange Commission’s public reference room located at 450 Fifth Street, N.W., Washington, D.C. 20549. Please call the Securities and Exchange Commission at 1-800-SEC-0330 for further information on the operation of such public reference room. You also can request copies of such documents, upon payment of a duplicating fee, by writing to the Securities and Exchange Commission at 450 Fifth Street, N.W., Washington, D.C. 20549. The Securities and Exchange Commission maintains a website that contains reports, proxy statements and other information regarding our company. The address of this website is http://www.sec.gov.

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission. The registration statement contains more information than this prospectus regarding us and our Common Stock, including certain exhibits and schedules. You can obtain a copy of the registration statement from the Securities and Exchange Commission at the address listed above or from the SEC’s Internet site.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The Securities and Exchange Commission requires us to “incorporate by reference” into this prospectus certain information we file with them, which means that we can disclose important information to you by referring you to those documents. The information we incorporate herein by reference is considered to be part of this prospectus and information that we file later with the Securities and Exchange Commission automatically will update and supersede such information. We incorporate herein by reference the documents listed below and any future filings we make with the Securities and Exchange Commission under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, prior to the termination of the offering of the securities covered by this prospectus, as amended:

(1) Our Annual Report on Form 10-KSB for the fiscal year ended December 31, 2002;

(2) Our Quarterly Reports on Form 10-QSB for the fiscal quarters ended March 31, 2003 and June 30, 2003;

(3) Our Current Reports on Form 8-K dated January 13, 2003, March 31, 2003, July 28, 2003, August 27, 2003, September 15, 2003, September 30, 2003 and October 14, 2003;

(4) The description of our Common Stock contained in our Registration Statement on Form 8-A filed with the Securities and Exchange Commission, including any amendments or reports filed for the purpose of updating that description; and

(5) All of our filings pursuant to the Exchange Act after the date of filing the initial registration statement and prior to effectiveness of the registration statement.

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You may request, orally or in writing, a copy of these filings (including exhibits to such filings that we have specifically incorporated by reference in such filings), at no cost, by contacting our executive offices at the following address:

Sontra Medical Corporation

10 Forge Parkway

Franklin, Massachusetts 02038

Attention: Chief Financial Officer

(508) 553-8850

You should rely only on the information contained in this prospectus, including information incorporated by reference as described above, or any prospectus supplement or that we have specifically referred you to. We have not authorized anyone else to provide you with different information. You should not assume that the information in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front of those documents or that any document incorporated by reference is accurate as of any date other than its filing date. You should not consider this prospectus to be an offer or solicitation relating to the securities in any jurisdiction in which such an offer or solicitation relating to the securities is not authorized. Furthermore, you should not consider this prospectus to be an offer or solicitation relating to the securities if the person making the offer or solicitation is not qualified to do so, or if it is unlawful for you to receive such an offer or solicitation.

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PROSPECTUS SUMMARY

This summary highlights important features of this offering and the information included or incorporated by reference in this prospectus. This summary does not contain all of the information that you should consider before investing in our Common Stock. You should read the entire prospectus carefully, especially the risks of investing in our Common Stock discussed under “Risk Factors.”

Sontra Medical Corporation

Sontra Medical Corporation is the pioneer of SonoPrep^®, a non-invasive ultrasound mediated skin permeation technology for medical and therapeutic applications including transdermal diagnostics and the enhanced delivery of drugs through the skin. The Company’s vision is for painless and continuous transdermal diagnosis and drug delivery that will improve patient outcome and reduce health care costs. These benefits will be realized with improved patient compliance to treatment, continuous diagnosis and data collection and new routes for continuous drug delivery. Our strategy is to leverage our ultrasonic skin permeation technology to develop short term commercialization opportunities and long term strategic partnerships.

Short term product development programs based on the SonoPrep^® skin permeation technology include:

• Enhanced transdermal delivery of topically applied drugs.

• Accelerated onset of action of currently approved transdermal drugs.

Long term strategic partnerships are being developed with market leaders in the following areas:

• Symphony^™ Diabetes Management System for continuous non-invasive blood glucose monitoring.

• Transdermal drug delivery of large molecules and biopharmaceuticals.

• Topical vaccination.

The ultrasound skin permeation technology was developed by our co-founders Dr. Joseph Kost and Dr. Robert Langer at the Massachusetts Institute of Technology’s Chemical and Bioengineering Laboratory. This technology was licensed and further advanced to the point of clinical use by us. In total, we own or license eleven issued US patents and six pending US patents. In addition, we license several related foreign patents and patent applications, and have sixteen foreign patent applications pending.

Company Information

Sontra Medical Corporation was formed through the merger of Sontra Medical, Inc. (“SMI”) and ChoiceTel Communications, Inc. in June 2002 (the “Merger”). Following the Merger, ChoiceTel Communications, Inc. changed its name to Sontra Medical Corporation and began operating in SMI’s line of business. SMI was incorporated in the State of Delaware on March 31, 1998.

Our principal executive offices are located at 10 Forge Parkway, Franklin, Massachusetts 02038, and our telephone number is (508) 553-8850. Our web site is located at www.sontra.com. We have not incorporated by reference into this prospectus the information on our website and

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you should not consider it to be a part of this document. Our website address is included in this document as an inactive textual reference only. Unless the context otherwise requires, the terms “Sontra,” “the Company,” “we,” “us” and “our” refer to Sontra Medical Corporation.

The Offering

Common Stock offered by selling shareholders	15,360,000 shares
Use of proceeds	Sontra will not receive any proceeds from the sale of shares in this offering. Upon any exercise of the warrants by payment of cash, however, we will receive the exercise price of the warrants, which is $1.50 per share for the warrants issued to the purchasers in the Private Placement and $1.20 per share for the warrants issued to the placement agent in the Private Placement.
Nasdaq SmallCap Market symbol	“SONTC”

All of the shares being offered by this prospectus are being offered by the selling shareholders listed herein. The selling shareholders identified in this prospectus, or their pledgees, donees, transferees or other successors-in-interest, may offer the shares or interests therein from time to time through public or private transactions at prevailing market prices, at prices related to prevailing market prices or at privately negotiated prices.

Recent Developments

Nasdaq Delisting Notice

Our Common Stock is currently listed for trading on the Nasdaq SmallCap Market. On June 18, 2003 we received a letter from Nasdaq stating that Sontra had failed to comply with the minimum $2.5 million stockholders’ equity requirement for continued listing set forth in Marketplace Rule 4310(c)(2)(B) and that as a result, our Common Stock is subject to delisting from the Nasdaq SmallCap Market. On July 31, 2003 we had a hearing with the Nasdaq Listing Qualifications Panel and on August 25, 2003, the Nasdaq Listings Qualifications Panel granted Sontra a conditional exception from Nasdaq’s minimum $2.5 million stockholders’ equity requirement for continued listing set forth in Marketplace Rule 4310(c)(2)(B). The exception received from Nasdaq is subject to certain conditions. We will be required to file with the Securities and Exchange Commission, on or before October 15, 2003, a balance sheet no older than 45 days prior to the filing evidencing stockholders’ equity of at least $2.5 million. In addition, we will be required to timely file our Form 10-QSB for the third quarter of 2003 showing stockholders’ equity of at least $2.5 million as of September 30, 2003. We will also be required to submit to Nasdaq, on or before January 30, 2004, an unaudited balance sheet and income statement for the fiscal year ending December 31, 2003 evidencing stockholders’ equity of at least $2.5 million. Finally, we will be required to timely file our Form 10-KSB for fiscal 2003 showing stockholders’ equity of at least $2.5 million as of December 31, 2003. Provided that Sontra is deemed to meet each of the conditions on a timely basis, our Common Stock will remain listed on the Nasdaq SmallCap Market. In the event that Sontra fails to meet any of the conditions, our Common Stock will be delisted from Nasdaq. In addition, effective at the opening of business on August 27, 2003, and continuing for the duration of the exception, our Common Stock will trade under the symbol “SONTC.” On October 14, 2003, we filed with the Securities and Exchange Commission a Current Report on Form 8-K with our balance sheet dated September 30, 2003 evidencing stockholders’ equity of at least $2.5 million.

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Private Placement

We have completed a private placement to selected qualified purchasers of units consisting of shares of our Series A Convertible Preferred Stock and Warrants to purchase shares of our Common Stock (the “Private Placement”). On September 15, 2003, we completed the initial closing of the Private Placement, providing Sontra with proceeds of approximately $2.9 million net of the placement agent fee. Individual investors, institutions and certain members of the Board of Directors purchased 3,139,167 shares of the Company’s Series A Convertible Preferred Stock, at a per share purchase price of $1.00. The investors also received warrants to purchase up to 3,139,167 shares of Common Stock.

On September 30, 2003, we completed the second closing of the Private Placement, providing Sontra with approximately $500,000 in additional proceeds, net of the placement agent fee. Investors purchased 535,000 shares of Series A Preferred Stock, at a per share purchase price of $1.00. The investors also received warrants to purchase up to 535,000 shares of Common Stock.

On October 14, 2003, we completed the final closing of the Private Placement, providing Sontra with approximately $3.1 million in additional proceeds, net of the placement agent fee. Investors purchased the remaining 3,325,833 shares of Series A Preferred Stock, at a per share purchase price of $1.00. The investors also received warrants to purchase up to 3,325,833 shares of Common Stock.

Each share of Series A Preferred Stock is initially convertible into one share of Common Stock, subject to adjustment in certain events. The holders of shares of Series A Preferred Stock are entitled to receive annual 8% dividends, payable in cash or shares of Common Stock. The Company has the right to convert the shares of Series A Preferred Stock in the event that the closing price of our Common Stock for twenty consecutive trading days is equal to or greater than $3.00 per share. The warrants issued to the purchasers in the Private Placement are exercisable at a per share price of $1.50 and expire no later than the fifth anniversary of their issuance date. In addition, we have the right to terminate the warrants, upon thirty days notice, in the event that the closing price of our Common Stock for twenty consecutive trading days is equal to or greater than $4.00 per share. The warrants shall be exercisable during such thirty-day notice period.

Each purchaser in the Private Placement also received certain pre-emptive rights to participate in future issuances, grants or sales of equity or equity-linked securities of the Company. Such pre-emptive rights are based upon the number of shares of Common Stock then held by the purchaser (on a fully-diluted basis) and are subject to customary exceptions. Each purchaser shall have the pre-emptive rights only for so long as such purchaser holds shares of Series A Preferred Stock or, if earlier, until the third anniversary of the grant of such rights.

In connection with the Private Placement, the placement agent received warrants to purchase an aggregate of 800,000 shares of Common Stock. Such placement agent warrants are exercisable at a per share price of $1.20 and expire no later than the fifth anniversary of their issuance date. In addition, we have the right to terminate the placement agent warrants, upon thirty days notice, in the event that the closing price of our Common Stock for twenty consecutive trading days is equal to or greater than $4.00 per share. The warrants shall be exercisable during such thirty-day notice period.

The Company also paid to the placement agent for its services in connection with the Private Placement a cash fee of seven percent of the proceeds raised in the Private Placement

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from institutional investors other than members of the Board of Directors of the Company and/or their respective affiliates (three percent in the event such institutional investors were referred by other brokers), a cash fee of ten percent of the proceeds raised in the Private Placement from other investors other than members of the Board of Directors of the Company and/or their respective affiliates, and a cash fee equal to three percent of the proceeds of the Private Placement raised from members of the Board of Directors of the Company and/or their respective affiliates. The Company agreed to pay the reasonable expenses incurred by the placement agent in connection with the Private Placement, subject to an aggregate limitation of $40,000. The placement agent also received a success fee in the form of a one-year consulting agreement with the Company paying an aggregate of $60,000.

We intend to use the net proceeds from the Private Placement and from any exercise of the warrants for product development, funding clinical trials, initial scale of manufacturing capacity, working capital and general corporate purposes.

On September 30, 2003, at a Special Meeting of Shareholders, our shareholders approved the issuance of shares of our Common Stock upon conversion of the Series A Preferred Stock and the exercise of the Common Stock Purchase Warrants in satisfaction of NASD Rules 4350(i)(l)(B) and (D).

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RISK FACTORS

If you purchase shares of our Common Stock, you will take on financial risk. In deciding whether to invest, you should carefully consider the following factors, the information contained in this prospectus and the additional information in our other reports on file with the Securities and Exchange Commission and in other documents incorporated by reference in this prospectus. The risks described below are not the only ones that we face. Additional risks not presently known to us or that we currently consider immaterial may also impair our business operations. Any of these risks could have a material and adverse effect on our business, financial condition or operating results. The trading price of our Common Stock could decline due to any of these risks, and you could lose all or part of your investment.

We have a history of operating losses, and we expect our operating losses to continue for the foreseeable future.

We have generated limited revenues and have had operating losses since our inception. Our historical accumulated deficit was approximately $17,555,000 as of June 30, 2003. It is possible that the Company will never generate any additional revenue or generate enough additional revenue to achieve profitability. Even if the Company reaches profitability, it may not be able to sustain or increase profitability. We expect our operating losses to continue for the foreseeable future as we continue to expend substantial resources to conduct research and development, feasibility and clinical studies, obtain regulatory approvals for specific use applications of our SonoPrep^® technology, identify and secure collaborative partnerships, and manage and execute our obligations in strategic collaborations.

Our independent accountants have noted concerns about our ability to continue as a going concern in their report on our audited financial statements for the year ended December 31, 2002, which may have an adverse impact on our ability to raise necessary additional capital and on our stock price.

The Company has generated limited revenue since inception (from an historical accounting perspective), and does not expect to generate revenues in the near future. Our development efforts to date have consumed and will continue to require substantial amounts of capital to complete the development of our SonoPrep^® technology and to meet other cash requirements in the future. Our current liabilities exceeded our current assets by $405,000 at June 30, 2003. We are implementing measures to decrease our operating expenses and are actively seeking to procure additional financing or investment, or strategic investment, adequate to fund our ongoing operations. However, raising capital has become increasingly difficult for many companies. Any future equity financing, if available, may result in substantial dilution to existing shareholders, and debt financing, if available, may include restrictive covenants or may require us to grant a lender a security interest in our assets. To the extent that we attempt to raise additional funds through third party collaborations and/or licensing arrangements, we may be required to relinquish some rights to our technologies or products currently in various stages of development, or grant licenses on terms that are not favorable to the Company. If the Company is unable to raise sufficient additional financing we will not be able to continue our operations.

Given these future capital requirements, our auditors have added a “going concern” paragraph to their audit report for our financial statements for the fiscal year ended December 31, 2002. A “going concern” paragraph with an audit opinion means that the auditor has identified certain conditions or events that indicate there could be substantial doubt about our ability to continue as a going entity for a period of at least one year from the date of the financial

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statements. The inclusion of this explanatory paragraph in the report of our auditors on our 2002 financial statements may have an adverse impact on our ability to raise necessary additional capital and on our stock price. We cannot assure you that we will be able to continue as a going concern. Even if we successfully raise adequate financing to continue as a going concern beyond December 31, 2003, we will need substantial additional capital to reach product commercialization and profitability. Any failure by the Company to timely procure additional financing or investment adequate to fund the Company’s ongoing operations, including planned product development initiatives and clinical studies, will have material adverse consequences on the Company’s business operations and as a result, on our consolidated financial condition, results of operations and cash flows.

We have received a delisting notice from Nasdaq because of our failure to meet the stockholders’ equity continued listing requirement.

Our Common Stock is currently listed for trading on the Nasdaq SmallCap Market. On June 18, 2003, we received a letter from Nasdaq stating that Sontra had failed to comply with the minimum $2.5 million stockholders’ equity requirement for continued listing set forth in Marketplace Rule 4310(c)(2)(B) and that as a result, our Common Stock is subject to delisting from the Nasdaq SmallCap Market. On July 31, 2003, we had a hearing with the Nasdaq Listing Qualifications Panel and on August 25, 2003, the Nasdaq Listings Qualifications Panel granted Sontra a conditional exception from Nasdaq’s minimum $2.5 million stockholders’ equity requirement for continued listing set forth in Marketplace Rule 4310(c)(2)(B). The exception received from Nasdaq is subject to certain conditions. We will be required to file with the Securities and Exchange Commission, on or before October 15, 2003, a balance sheet no older than 45 days prior to the filing evidencing stockholders’ equity of at least $2.5 million. In addition, we will be required to timely file our Form 10-QSB for the third quarter of 2003 showing stockholders’ equity of at least $2.5 million as of September 30, 2003. We will also be required to submit to Nasdaq, on or before January 30, 2004, an unaudited balance sheet and income statement for the fiscal year ending December 31, 2003 evidencing stockholders’ equity of at least $2.5 million. Finally, we will be required to timely file its Form 10-KSB for fiscal 2003 showing stockholders’ equity of at least $2.5 million as of December 31, 2003. Provided that Sontra is deemed to meet each of the conditions on a timely basis, our Common Stock will remain listed on The Nasdaq SmallCap Market. In the event that Sontra fails to meet any of the conditions, our Common Stock will be delisted from Nasdaq. If the Company’s Common Stock is delisted from the Nasdaq SmallCap Market, it may trade on the over-the-counter market, which may be a less liquid market. In such case, our stockholders’ ability to trade, or obtain quotations of the market value of, shares of Sontra’s Common Stock would be severely limited because of lower trading volumes and transaction delays. These factors could contribute to lower prices and larger spreads in the bid and ask prices for our Common Stock. In addition, the delisting of the Common Stock from the Nasdaq SmallCap Market would significantly impair our ability to raise capital in the public markets in the future.

The price of the Company’s stock may be volatile and trading in the stock is likely to be limited.

The trading price of the Company’s Common Stock has fluctuated in the past and is expected to continue to do so in the future as a result of a number of factors, many of which are outside the Company’s control. Historically, the volume of trading in the Company’s Common Stock has been limited and fluctuations in price have been volatile.

In addition, the stock market has experienced price and volume fluctuations that have affected the market prices of many companies, and that have often been unrelated or disproportionate to the operating performance of these companies. These broad market fluctuations could adversely affect the market price of the Company’s Common Stock. In the

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past, following periods of volatility in the market price of a particular company’s securities, securities class action litigation has often been brought against that company. Potential securities class action litigation brought against the Company could result in substantial costs and a diversion of the Company’s management’s attention and resources.

We have limited publicly available historical financial information, which makes it difficult to evaluate our business.

Because limited publicly available historical financial information is available on our business, it may be difficult to evaluate our business and prospects. Our business and prospects must be considered in light of the substantial risks, expenses, uncertainties and difficulties encountered by entrants into the medical device industry, which is characterized by increasingly intense competition and a high failure rate. To date, we have engaged primarily in research and development efforts, prototype development and testing, and human clinical feasibility studies. Our results of operations will depend on, among other things, the following factors:

• research and development activities and outcomes;

• results of feasibility and pre-clinical studies;

• the ability to enter into collaborative agreements;

• the timing of payments, if any, under future collaborative agreements; and

• costs related to obtaining, defending and enforcing patents.

The development and commercialization of our potential products, including the SonoPrep^® device and the Symphony^™ Diabetes Management System, will require the formation of strategic partnerships with third parties, as well as substantial capital expenditures either by the Company or the strategic partner of the Company on research, regulatory compliance, sales and marketing and manufacturing.

Our future success is dependent upon successful collaborations with strategic partners.

Our future success is dependent upon our ability to selectively enter into and maintain collaborative arrangements with leading medical device and pharmaceutical companies, such as Bayer Healthcare LLC (“Bayer”). On July 28, 2003, Sontra and Bayer executed a definitive license agreement pursuant to which Sontra granted to Bayer an exclusive worldwide right and license of Sontra’s intellectual property rights to make, have made, use, import and sell the Symphony Diabetes Management System. Sontra and Bayer are also expected to enter into one or more additional agreements to continue the joint development of the Symphony Diabetes Management System. We may not be able to enter into any additional collaborative arrangements on acceptable terms, if at all. If we are not able to collaborate with Bayer or additional partners, the business, financial condition and results of operations of the Company could be materially adversely affected.

Even if we were to enter into a collaborative arrangement, there can be no assurance that the financial condition or results of operations of the Company will significantly improve. The risks involved with collaborating with strategic partners include, but are not limited to, the following:

• such collaborative arrangements could terminate upon the expiration of certain notice periods;

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• funding by collaborative partners may be dependent upon the satisfaction of certain goals or “milestones” by certain specified dates, the realization or satisfaction of which may be outside of our control;

• collaborative partners may retain a significant degree of discretion regarding the timing of these activities and the amount and quality of financial, personnel and other resources that they devote to these activities;

• disputes may arise between the Company and any future collaborative partner regarding their respective rights and obligations under the collaborative arrangements, which may be costly; and

• any future collaborative partner may not be able to satisfy its obligations under its arrangement with the Company or may intentionally or unintentionally breach its obligations under the arrangement.

All of our products are in initial stages of development, and we face risks of failure inherent in developing products based on new technologies.

Our products under development have a high risk of failure because they are in the early stages of development. To date, we have only tested the feasibility of our SonoPrep^® technology for various applications, including glucose monitoring, transdermal drug delivery and certain aesthetic applications. Although the Company has filed a 510(k) application seeking marketing clearance from the FDA for our SonoPrep^® device for use in electrophysiology applications, none of the products currently being developed by the Company have received regulatory approval or clearance for commercial sale. Substantial expenditures for additional research and development, including feasibility studies, pre-clinical studies and clinical testing, the establishment of collaborative partnerships and regulatory, manufacturing, sales and marketing activities by collaborative partners will be necessary before commercial production of any of our technologies or their incorporation into products of third parties. Our future prospects are substantially dependent on forming collaborative partnerships, further developing our products and obtaining favorable results from pre-clinical studies and clinical trials and satisfying regulatory standards and approvals required for the market introduction of the SonoPrep^® device and Symphony^™ Diabetes Management System.

There can be no assurance that the Company or any strategic partner of the Company will not encounter unforeseen problems in the development of the SonoPrep^® technology, or that we or any such strategic partner will be able to successfully address the problems that do arise. In addition, there can be no assurance that any of our potential products will be successfully developed, proven safe and efficacious in clinical trials, meet applicable regulatory standards, be capable of being produced in commercial quantities at acceptable costs, be eligible for third-party reimbursement from governmental or private insurers, be successfully marketed or achieve market acceptance. If any of our development programs are not successfully completed, required regulatory approvals or clearances are not obtained, or potential products for which approvals or clearances are obtained are not commercially successful, our business, financial condition and results of operations would be materially adversely affected.

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Failure to obtain necessary regulatory approvals will prevent the Company or our collaborators from commercializing our products under development.

The design, manufacturing, labeling, distribution and marketing of our potential products will be subject to extensive and rigorous government regulation in the United States and certain other countries. The process of obtaining and maintaining required regulatory clearance and approvals in the United States is lengthy, expensive and uncertain. In order for us to market our potential products in the United States, we must obtain clearance by means of a 510(k) pre-market notification, or approval by means of a pre-market approval (“PMA”) application, from the United States Food and Drug Administration (“FDA”). In November 2002, we filed a 510(k) application seeking marketing clearance from the FDA for our SonoPrep^® device for use in electrophysiology applications. In order to obtain marketing clearance for our Symphony^™ Diabetes Management System, we will be required to file a PMA application that demonstrates the safety and effectiveness of the product. The PMA process is more rigorous and lengthier than the 510(k) clearance process and can take several years from initial filing and require the submission of extensive supporting data and clinical information.

Even if we receive 510(k) clearance or PMA approval, there can be no assurance that the FDA will not impose strict labeling or other requirements as a condition of our clearance or approval, any of which could limit our ability to market our products under development. Further, if we wish to modify a product after FDA clearance or approval, including changes in indications or other modifications that could affect safety and efficacy, additional clearances or approvals could be required from the FDA. Any request by the FDA for additional data or any requirement by the FDA that we conduct additional clinical studies could significantly delay the commercialization of our products and require us to make substantial additional research, development and other expenditures by the Company. Similarly, any labeling or other conditions or restrictions imposed by the FDA on the marketing of our potential products could hinder the Company’s ability to effectively market these products.

A substantial portion of the intellectual property used by the Company is owned by the Massachusetts Institute of Technology.

We have an exclusive world-wide license to use and sell certain technology owned by the Massachusetts Institute of Technology (MIT) related to our ultrasound-mediated skin permeation technology. This license, which includes eight issued patents in the United States, three issued foreign patents, one pending U.S. patent and three pending foreign patent applications, comprises a substantial portion of our patent portfolio relating to our technology.

While, under the license agreement, we have the right to advise and cooperate with MIT in the prosecution and maintenance of the foregoing patents, we do not control the prosecution of such patents or the strategy for determining when such licensed patents should be enforced. Instead, the Company relies upon MIT to determine the appropriate strategy for prosecuting and enforcing these patents. If MIT does not adequately protect or enforce our patent rights, our ability to manufacture and market our products, currently in various stages of development, would be adversely affected.

We will need to obtain and protect the proprietary information on which our SonoPrep^® technology relies.

We have an exclusive license from MIT on eight issued patents in the United States, three issued foreign patents, one pending U.S. patent and three pending foreign patent applications, and

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as of May 15, 2003, we owned three issued patents and seven pending patent applications in the United States and sixteen PCT pending foreign applications. We can provide no assurance that patents will be issued from the patent applications, or, if issued, that they will be issued in a form that will be advantageous to the Company.

There can be no assurance that one or more of the patents owned or licensed by the Company will not be successfully challenged, invalidated or circumvented or that we will otherwise be able to rely on such patents for any reason. If any of our patents or any patents licensed from MIT are successfully challenged or our right or ability to manufacture our future products (if successfully developed and commercialized) were to be limited, our ability to manufacture and market these products could be adversely affected, which would have a material adverse effect upon our business, financial condition and results of operations.

In addition to patent protection, we rely on a combination of copyright, trade secret and trademark laws, and nondisclosure, confidentiality agreements and other contractual restrictions to protect our proprietary technology. However, these legal means afford only limited protection and may not adequately protect the rights or competitive advantage of the Company. We may not be able to prevent the unauthorized disclosure or use of our technical knowledge or other trade secrets by our employees. Nondisclosure and confidentiality agreements with third parties may be breached, and there is no assurance that the Company would have adequate remedies for any such breach.

If we fail to protect our intellectual property rights, our competitors may take advantage of our ideas and compete directly against the Company. There can be no assurance that competitors, many of whom have substantial resources and have made substantial investments in competing technologies, will not seek to apply for and obtain patents that limit our ability to make, use and sell our potential products either in the United States or in foreign markets. Furthermore, if our intellectual property is not adequately protected, our competitors may be able to use our intellectual property to enhance their products and compete more directly with the Company, which could prevent us from entering our products into the market or result in a decrease in our eventual market share.

We have limited manufacturing experience, which could limit our growth.

To successfully commercialize our SonoPrep^® device and Symphony^™ Diabetes Management System, we will have to manufacture or engage others to manufacture the particular device in compliance with regulatory requirements. We have limited manufacturing experience that would enable us to make products in the volumes that would be necessary for us to achieve significant commercial sales, and there can be no assurance that we will be able to establish and maintain reliable, efficient, full scale manufacturing at commercially reasonable costs, in a timely fashion. Difficulties we encounter in manufacturing scale-up, or our failure to implement and subsequently maintain our manufacturing facilities in accordance with good manufacturing practice regulations, international quality standards or other regulatory requirements, could result in a delay or termination of production. Companies, and especially small companies in the medical device field, often encounter these types of difficulties in scaling up production, including problems involving production yield, quality control and assurance, and shortages of qualified personnel.

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We may be subject to litigation or other proceedings relating to our patent rights.

The medical device industry has experienced extensive litigation regarding patents and other intellectual property rights. In addition, the United States Patent and Trademark Office may institute litigation or interference proceedings against the Company. The defense and prosecution of intellectual property proceedings are both costly and time consuming.

Litigation may be necessary to enforce patents issued to the Company, to protect trade secrets or know how owned by or licensed to the Company or to determine the enforceability, scope and validity of the proprietary rights of others. Any litigation or interference proceedings involving the Company may require us to incur substantial legal and other fees and expenses. Such proceedings would also be time consuming and can be a significant distraction for employees and management, resulting in slower product development and delays in commercialization. In addition, an adverse determination in litigation or interference proceedings could subject the Company to significant liabilities to third parties, require us to obtain licenses from third parties or prevent us from selling our products, once developed, in certain markets, or at all, which would have a material adverse effect on our business, financial condition and results of operations.

Our potential markets are highly competitive and most participants are larger, better capitalized, and more experienced than Sontra.

The industries in which our potential products may eventually be marketed are intensely competitive, subject to rapid change and significantly affected by new product introductions. Our Symphony^™ Diabetes Management System will compete directly with glucose monitoring products manufactured by Roche Diagnostics, LifeScan, Inc., a division of Johnson & Johnson, Bayer Corporation, MediSense, a division of Abbott Laboratories, Cygnus, Inc., SpectRx and TheraSense, Inc. The Company’s SonoPrep^® device will also compete with numerous companies developing drug delivery products such as Nektar Therapeutic Systems, Inc., Alkermes, Inc., Bioject, Inc., PowderJect Pharmaceuticals PLC, Antares Pharma, Inc., Becton Dickinson & Co., Aerogen, Inc. ALZA Corporation, a division of Johnson and Johnson, Norwood Abbey Limited and 3M Company.

These companies are already producing and marketing glucose monitoring or drug delivery products, are either publicly traded or a division of a publicly traded company, and enjoy several competitive advantages over the Company. In addition, several our competitors have products in various stages of development and commercialization similar to our SonoPrep^® device and Symphony^™ Diabetes Management System. At any time, these companies and others may develop products that compete directly with our proposed product concepts. In addition, many of our competitors have resources allowing them to spend significantly greater funds for the research, development, promotion and sale of new or existing products, thereby allowing them to respond more quickly to new or emerging technologies and changes in customer requirements. For all of the foregoing reasons, we may not be able to compete successfully against our current and future competitors. If any of our competitors succeeds in developing a commercially viable product and obtaining government approval, the business, financial condition and results of operations of the Company would be materially adversely affected.

We operate in an industry with significant product liability risk.

Our business will expose us to potential product liability claims that are inherent in the testing, production, marketing and sale of human diagnostic and ultrasonic transdermal drug

- 15 -

delivery products. While we intend to take steps to insure against these risks, there can be no assurance that we will be able to obtain insurance in amounts or scope sufficient to provide us with adequate coverage against all potential liabilities. Our current product liability insurance provides for coverage in the amount of $2,000,000 and upon successful development and commercialization of our products, we intend to obtain product liability insurance in the amount of $5,000,000. A product liability claim in excess of our product liability insurance would have to be paid out of our cash reserves, if any, and would harm our reputation in the industry and adversely affect our ability to raise additional capital.

Our management has significant influence over the control of Sontra.

Our officers and directors beneficially own approximately 48.8% of the outstanding shares of our Common Stock. Accordingly, our officers and directors will have significant influence over the outcome of any corporate transaction or other matters submitted to the shareholders for approval, including mergers, consolidations and the sale of all or substantially all of the Company’s assets, and also could prevent or cause a change in control. Third parties may be discouraged from making a tender offer or bid to acquire the Company because of this concentration of ownership.

If we are unable to retain or hire additional key personnel, we may not be able to sustain or grow our business.

Our future success will depend upon our ability to successfully attract and retain key scientists, engineers and other highly skilled personnel. With the exception of Dr. Thomas W. Davison, our President and Chief Executive Officer, and Sean Moran, our Chief Financial Officer, our employees are at-will and not subject to employment contracts and may terminate their employment with the Company at any time. In addition, our current management team is understaffed and has very limited experience managing a public company subject to the Securities and Exchange Commission’s periodic reporting obligations. Hiring qualified management and technical personnel will be difficult due to the limited number of qualified professionals in the work force in general and the intense competition for these types of employees in the medical device industry, in particular. We have in the past experienced difficulty in recruiting qualified personnel and there can be no assurance that we will be successful in attracting and retaining additional members of management if the business begins to grow. Failure to attract and retain personnel, particularly management and technical personnel would materially harm our business, financial condition and results of operations.

Our stock price has been volatile and may fluctuate in the future.

The trading price of our Common Stock may fluctuate significantly. This price may be influenced by many factors, including:

• our performance and prospects;

• the depth and liquidity of the market for our Common Stock;

• investor perception of us and the industry in which we operate;

• changes in earnings estimates or buy/sell recommendations by analysts;

• general financial and other market conditions; and

• domestic and international economic conditions.

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Public stock markets have experienced, and are currently experiencing, extreme price and trading volume volatility, particularly in the technology and life sciences sectors of the market. This volatility has significantly affected the market prices of securities of many technology companies for reasons frequently unrelated to or disproportionately impacted by the operating performance of these companies. These broad market fluctuations may adversely affect the market price of our Common Stock. In addition, fluctuations in our stock price may have made our stock attractive to momentum, hedge or day-trading investors who often shift funds into and out of stocks rapidly, exacerbating price fluctuations in either direction particularly when viewed on a quarterly basis.

Securities we issue to fund our operations could dilute your ownership or otherwise adversely affect our shareholders.

We will likely need to raise additional funds through public or private debt or equity financings to fund our operations. If we raise funds by issuing equity securities, the percentage ownership of current stockholders will be reduced and the new equity securities may have rights senior to those of the shares of our Common Stock. If we raise funds by issuing debt securities, we may be required to agree to covenants that substantially restrict our ability to operate our business. We may not obtain sufficient financing on terms that are favorable to investors or us. We may delay, limit or eliminate some or all of our proposed operations if adequate funds are not available.

The availability of preferred stock for issuance may adversely affect our shareholders.

Our Articles of Incorporation, as amended, authorize our Board of Directors to fix the rights, preferences and privileges of, and issue up to 10,000,000 shares of, preferred stock with voting, conversion, dividend and other rights and preferences that could adversely affect the voting power or other rights of our shareholders. An aggregate of 7,000,000 shares of Series A Preferred Stock are currently issued and outstanding. The issuance of additional preferred stock or rights to purchase preferred stock may have the effect of delaying or preventing a change in control of the Company. In addition, the possible issuance of additional preferred stock could discourage a proxy contest, make more difficult the acquisition of a substantial block of the Company’s Common Stock or limit the price that investors might be willing to pay for shares of the Company’s Common Stock.

Anti-takeover effects of Minnesota law could discourage, delay or prevent a change in control.

As a publicly traded company, we are prohibited by the Minnesota Business Corporation Act, except under certain specified circumstances, from engaging in any merger, significant sale of stock or assets or business combination with any shareholder or group of shareholders who own at least 10% of our Common Stock.

SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

This prospectus includes and incorporates forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. All statements, other than statements of historical facts, included or incorporated in this prospectus regarding our strategy, future operations, financial position, future revenues, projected costs, prospects, plans and objectives of management are forward-looking statements. The words “anticipates,” “believes,” “estimates,” “expects,” “intends,” “may,” “plans,” “projects,” “will,” “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. We cannot guarantee that we actually will achieve the plans, intentions or expectations disclosed in our forward-looking statements and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and

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expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included or incorporated in this prospectus, particularly under the heading “Risk Factors,” that we believe could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make. Except as otherwise required by law, we do not assume any obligation to update any forward-looking statements.

USE OF PROCEEDS

We will not receive any proceeds from the sale of shares by the selling shareholders. The selling shareholders will pay any underwriting discounts and commissions and expenses incurred by the selling shareholders for brokerage, accounting, tax or legal services or any other expenses incurred by the selling shareholders in disposing of the shares. We will bear all other costs, fees and expenses incurred in effecting the registration of the shares covered by this prospectus, including, without limitation, all registration and filing fees, Nasdaq listing fees, blue sky registration and filing fees, and fees and expenses of our counsel and our accountants.

A portion of the shares covered by this prospectus are, prior to their resale pursuant to this prospectus, issuable upon exercise of Common Stock Purchase Warrants. Upon any exercise of the warrants by payment of cash, we will receive the exercise price of the warrants, which is $1.50 per share for the warrants issued to the purchasers in the Private Placement and $1.20 per share for the warrants issued to the placement agent in the Private Placement. To the extent we receive cash upon any exercise of the warrants, we expect to use that cash for general corporate purposes.

SELLING SHAREHOLDERS

The shares of Common Stock being sold by the selling shareholders consist of:

• 7,560,000 shares of our Common Stock issuable upon conversion of the shares of Series A Preferred Stock issued to the purchasers in the Private Placement, including our estimate of the maximum number of shares issuable as a result of the conversion of accrued dividends on the shares of Series A Preferred Stock;

• 7,000,000 shares of our Common Stock issuable upon exercise of the Common Stock Purchase Warrants issued to the purchasers in the Private Placement; and

• 800,000 shares of our Common Stock issuable upon exercise of the Common Stock Purchase Warrants issued to the placement agent in the Private Placement.

In accordance with the registration rights granted to the selling shareholders, Sontra has filed with the Securities and Exchange Commission a registration statement on Form S-3, of which this prospectus forms a part, with respect to the resale or other disposal of the shares of Common Stock offered by this prospectus or interests therein from time to time on the Nasdaq SmallCap Market, in privately negotiated transactions or otherwise. Sontra has also agreed to prepare and file amendments and supplements to the registration statement to the extent necessary to keep the registration statement effective until the shares are no longer required to be registered for the resale thereof by the selling shareholders.

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The actual number of shares of Common Stock covered by this prospectus, and included in the registration statement of which this prospectus is a part, includes additional shares of Common Stock that may be issued as a result of stock splits, stock dividends, reclassifications, recapitalizations, combinations or similar events.

Based on information provided to us by the selling shareholders, the following table sets forth ownership and registration information regarding the shares held by the selling shareholders, including: (1) the name of each selling shareholder, (2) the number of shares of our Common Stock beneficially owned by each selling shareholder, including the number of shares purchasable upon the conversion of the shares of Series A Preferred Stock and the exercise of the Common Stock Purchase Warrants held by the selling shareholder, (3) the maximum number of shares of Common Stock which the selling shareholders can sell pursuant to this prospectus, and (4) the number and percentage of shares of Common Stock that the selling shareholders would own if they sold all their shares registered by this prospectus. Each selling shareholder will receive all of the net proceeds from the sale of its shares of Common Stock offered by this prospectus. Unless otherwise indicated below, to our knowledge, all selling shareholders named in the table have sole voting and investment power with respect to their shares of Common Stock, except to the extent authority is shared by spouses under applicable law. The inclusion of any shares in this table does not constitute an admission of beneficial ownership for the selling shareholder named below.

			Shares of Common Stock Beneficially Owned After Offering(1)
Name of Selling Shareholder	Number of Shares of Common Stock Beneficially Owned Prior to Offering(2)	Number of Shares of Common Stock Being Offered(2)	Number	Percentage
Xmark Fund, Ltd.(3)(5)	638,334	638,334	0	—
Xmark Fund, L.P.(4)(5)	361,666	361,666	0	—
Constable Capital LLC	771,270	770,000	1,270	*	%
Constable Capital QP, LLC	230,380	230,000	380	*	%
Wigley Irrevocable Trust 1993	900,000	900,000	0	—
OTAPE Investments LLC	800,000	800,000	0	—
Jeffrey Paul Dauenhauer	700,000	700,000	0	—
Alpha Capital AG	500,000	500,000	0	—
SDS Merchant Fund, LP	500,000	500,000	0	—
Kenneth A. Steel, Jr.	500,000	500,000	0	—
Alex Tringas	460,000	460,000	0	—
Focus Capital L.P.	400,000	400,000	0	—
Vincent Young	400,000	400,000	0	—
CrossCap Partners LP	300,000	300,000	0	—
Thomas F. Kloberg	300,000	300,000	0	—
K.A. Steel Chemicals Inc.	300,000	300,000	0	—
AIG DKR Soundshore Private Investors Holding Fund Ltd.	250,000	250,000	0	—
Allan Lyons	250,000	250,000	0	—
TerraDek Lighting, Inc.	250,000	250,000	0	—

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Brophy & Phillips Co., Inc.	220,000		220,000	0		—
Robert C. Anderson	200,000		200,000	0		—
Essex Woodlands Health Ventures Fund IV, L.P.	1,603,429		200,000	1,403,429		5.8	%
Thomas and Patricia Burkard	200,000		200,000	0		—
Troy J. Rodriguez	200,000		200,000	0		—
Karl Scheil	200,000		200,000	0		—
Michael R. Wigley	1,184,709	(6)	200,000	984,709	(6)	4.0	%
Allen Crosswell	150,000		150,000	0		—
Michael R. Hamblett	140,000		140,000	0		—
Steven Oliveira	140,000		140,000	0		—
Kent Algotsson	100,000		100,000	0		—
Peter Habib	100,000		100,000	0		—
Isaac Kodsi	100,000		100,000	0		—
Kevin McDermott	100,000		100,000	0		—
Anthony R. Paniccia	100,000		100,000	0		—
Sabbatical Ventures, LLC	100,000		100,000	0		—
David R. Shaub, Jr.	100,000		100,000	0		—
James C. Taylor	100,000		100,000	0		—
John J. Tringas	100,000		100,000	0		—
Stephen P. Boger D.D.S.	126,666		86,666	40,000		*	%
James Nordlie	70,000		70,000	0		—
Gary S. Kohler	891,185	(7)	66,668	824,517	(7)	3.4	%
Robert S. Langer	600,036	(8)	66,666	533,370	(8)	2.2	%
James R. McNab, Jr.	607,822	(9)	60,000	547,822	(9)	2.2	%
Sam Bolton	50,000		50,000	0		—
Leilaly Chang	50,000		50,000	0		—
Dr. and Mrs. Richard D. Cornell	50,000		50,000	0		—
David Habib	50,000		50,000	0		—
Joseph C. Hubbard	50,000		50,000	0		—
George G. Hunt	50,000		50,000	0		—
David and Marsha Kaplan	50,000		50,000	0		—
Scott L. and Gwendelyn Korney	50,000		50,000	0		—
Jack Lahav	50,000		50,000	0		—
Ilana Lahav and Jack Lahav	50,000		50,000	0		—
Lili Lahav and Jack Lahav	50,000		50,000	0		—
Shira Lahav and Jack Lahav	50,000		50,000	0		—
Laureen M. Lenahan	50,000		50,000	0		—
Claudio Lishman	50,000		50,000	0		—
Mack Family Trust	50,000		50,000	0		—
G. Kenneth McCart	50,000		50,000	0		—
Daniel C. McCauley	50,000		50,000	0		—
Arie Mrejen	50,000		50,000	0		—
Dennis Mullally	50,000		50,000	0		—
Robert Myers	50,000		50,000	0		—
Eric Nelson	50,000		50,000	0		—
Michael and Doris Panza	50,000		50,000	0		—
Andy Pashby	50,000		50,000	0		—
Barry Berman Rutenberg	50,000		50,000	0		—
Daniel Saro	50,000		50,000	0		—
Anthony J. Spatacco, Jr.	50,000		50,000	0		—

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David C. Stolp	50,000	50,000	0	—
Howard Treitman and Jay Treitman	50,000	50,000	0	—
Phillip Whittaker	50,000	50,000	0	—
Elizabeth A. Wigley UGMA Michael R. Wigley	50,000	50,000	0	—
Richard Feinberg	40,000	40,000	0	—
Great Plains Properties, Inc.	40,000	40,000	0	—
Mark Lymberopolous	40,000	40,000	0	—
Dewayne J. and Agnes Vick	40,000	40,000	0	—
Alexandra L. Wigley UGMA Michael R. Wigley	30,000	30,000	0	—
Kathryn K. Wigley UGMA Michael R. Wigley	30,000	30,000	0	—
Dennis L. Vick	30,000	30,000	0	—
Arrow Leather Finishing, Inc.	25,000	25,000	0	—
David Bennett	25,000	25,000	0	—
Fairwinds, Inc.	25,000	25,000	0	—
Bernice B. Harray	25,000	25,000	0	—
Hadassah Keynan and Irene Nussbaum	25,000	25,000	0	—
Paul Mauerhan	25,000	25,000	0	—
Paul H. Scherf, Jr.	25,000	25,000	0	—
Peter Tocci	25,000	25,000	0	—
Richard Dodds	20,000	20,000	0	—
Timothy Fox	20,000	20,000	0	—
Michael J. Maloney	20,000	20,000	0	—
Clifford L. Olson	20,000	20,000	0	—
Peter L. Scherer	20,000	20,000	0	—
Pamela and Michael Sime	20,000	20,000	0	—
Randy Stille	20,000	20,000	0	—
Dawson James Securities, a Division of Viewtrade Financial	800,000	800,000	0	—

* Less than 1%

(1) We do not know when or in what amounts a selling shareholder may dispose of the shares or interests therein. The selling shareholders may choose not to dispose of any or all of the shares offered by this prospectus. Because the selling shareholders may offer all or some of the shares or interests therein pursuant to this offering, and because, to our knowledge, there are currently no agreements, arrangements or understandings with respect to the sale of any of the shares, we cannot estimate the number of the shares that will be held by the selling shareholders after completion of the offering. However, for purposes of this table, we have assumed that, after completion of the offering, none of the shares covered by this prospectus will be held by the selling shareholders.

(2) Does not include the shares potentially issuable to each selling shareholder as a result of the conversion of accrued dividends on the shares of Series A Preferred Stock. Such dividends accrue on a daily basis from the date of issuance of the shares of Series A Preferred Stock at an annual rate of 8%. At our election, we may elect to pay such dividends in cash or in shares of our Common Stock. The actual number of shares to be issued cannot be determined until the conversion date.

(3) Xmark Fund, Ltd., a Cayman Islands exempted company (“Xmark Ltd.”), is a private investment fund that is owned by its investors and managed by Brown Simpson Asset Management, LLC, a New York limited liability company. Brown Simpson Asset Management, LLC, of which Mitchell D. Kaye is the managing member, has voting and investment control over the shares owned by Xmark Ltd. The number of shares beneficially owned by Xmark Ltd. represents (i) 319,167 shares of our Series A Convertible Preferred Stock (the “Xmark Ltd. Series A Preferred”), which, subject to certain restrictions contained therein, may be converted into 319,167 shares of our Common Stock, at a conversion price of $1.00 per share, which conversion price is subject to adjustment as set forth in the terms of the Series A Preferred Stock, and (ii) warrants (the “Xmark Ltd. Warrants”) which, subject to certain restrictions contained therein, entitle Xmark Ltd. to purchase up to an aggregate of 319,167 shares of Common Stock at an exercise price of $1.50 per share, which exercise price is subject to adjustment as set forth in the Xmark Ltd. Warrants.

(4) Xmark Fund, L.P., a Delaware limited partnership (“Xmark LP”), is a private investment fund that is owned by its investors and managed by its general partner, Brown Simpson Capital, LLC, a New York limited liability company. Brown Simpson Capital, LLC, of which Mitchell D. Kaye is the managing member, has voting and investment control over the shares owned by Xmark LP. The number of shares beneficially owned by Xmark LP represents (i) 180,833 shares of our Series A Convertible Preferred Stock (the “Xmark LP Series A Preferred,” and together with the Xmark Ltd. Series A Preferred, the “Xmark Series A Preferred”), which, subject to certain restrictions contained therein, may be converted into 180,833 shares of our Common Stock, at a conversion price of $1.00 per share, which conversion price is subject to adjustment as set forth in the terms of the Series A Preferred Stock, and (ii) warrants (the “Xmark LP Warrants,” and together with the Xmark Ltd. Warrants, the “Xmark Warrants”) which, subject to certain restrictions contained therein, entitle Xmark Ltd. to purchase an aggregate of up to 180,833 shares of our Common Stock at an exercise price of $1.50 per share, which exercise price is subject to adjustment as set forth in the Xmark LP Warrants.

(5) As of October 15, 2003, the aggregate number of shares of our Common Stock into which the Xmark Series A Preferred were convertible and the Xmark Warrants were exercisable was 1,000,000.

(6) Includes 309,166 shares that may be acquired within 60 days upon the exercise of stock options held by Mr. Wigley, and 106,800 shares held by Mr. Wigley as custodian for the benefit of his children.

(7) Includes 67,500 shares that may be acquired within 60 days upon the exercise of stock options held by Mr. Kohler, and 40,000 shares held by Mr. Kohler as custodian for the benefit of his children.

(8) Includes 39,635 shares that may be acquired within 60 days upon the exercise of stock options held by Mr. Langer, and 28,905 shares held by Laura Langer as custodian for Dr. Langer’s minor children.

(9) Includes 54,087 shares that may be acquired within 60 days upon the exercise of stock options held by Mr. McNab, and 106,918 shares that are held by the J.R. and M.W. McNab Family LLC.

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The Wigley Irrevocable Trust 1993 is a trust for the benefit of children of Michael R. Wigley, a member of the Board of Directors of the Company. Elizabeth Wigley, Alexandra Wigley and Kathryn Wigley are children of Mr. Wigley. Mr. Wigley is the Chairman of the Board of TerraDek Lighting, Inc. (“TerraDek”). Mr. Wigley and his wife are the majority shareholders of TerraDek. Mr. Wigley is the Chairman of the Board, President and Chief Executive Officer of Great Plains Properties, Inc. (“Great Plains”). Mr. Wigley and his wife are the majority shareholders of Great Plains. Mr. Wigley’s wife is also a director of Great Plains. Essex Woodland Health Ventures Fund IV, L.P. (“Essex”) holds in excess of 10% of the issued and outstanding shares of the Company’s Common Stock. Martin P. Sutter, a managing member of Essex Woodlands Health Ventures Fund IV, L.L.C., the general partner of Essex, is a member of the Board of Directors of the Company. Gary S. Kohler, Robert S. Langer and James R. McNab, Jr. are members of the Board of Directors of the Company. For a description of the Private Placement, see “Prospectus Summary—Recent Developments—Private Placement.”

Other than as set forth in the immediately preceding paragraph and in the table above, none of the selling shareholders has held any position or office with, and has not otherwise had a material relationship with, the Company or any of our subsidiaries within the past three years.

PLAN OF DISTRIBUTION

We are registering the shares of Common Stock on behalf of the selling shareholders. Sales of shares may be made by selling shareholders, including their respective donees, transferees, pledgees or other successors-in-interest directly to purchasers or to or through underwriters, broker-dealers or through agents. Sales may be made from time to time on the Nasdaq SmallCap Market, any other exchange upon which our shares may trade in the future, in the over-the-counter market or otherwise, at market prices prevailing at the time of sale, at prices related to market prices, or at negotiated or fixed prices. The shares may be sold by one or more of, or a combination of, the following:

• a block trade in which the broker-dealer so engaged will attempt to sell the shares as agent but may position and resell a portion of the block as principal to facilitate the transaction (including crosses in which the same broker acts as agent for both sides of the transaction);

• purchases by a broker-dealer as principal and resale by such broker-dealer, including resales for its account, pursuant to this prospectus;

• ordinary brokerage transactions and transactions in which the broker solicits purchases;

• through options, swaps or derivatives;

• in privately negotiated transactions;

• in making short sales or in transactions to cover short sales; and

• put or call option transactions relating to the shares.

The selling shareholders may effect these transactions by selling shares directly to purchasers or to or through broker-dealers, which may act as agents or principals. These broker-dealers may receive compensation in the form of discounts, concessions or commissions from the selling shareholders and/or the purchasers of shares for whom such broker-dealers may act as agents or to whom they sell as principals, or both (which compensation as to a particular broker-dealer might be in excess of customary commissions). The selling shareholders have advised us that they have not entered into any agreements, understandings or arrangements with any underwriters or broker-dealers regarding the sale of their securities.

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The selling shareholders may enter into hedging transactions with broker-dealers or other financial institutions. In connection with those transactions, the broker-dealers or other financial institutions may engage in short positions or other derivative transactions relating to the shares of our Common Stock or of securities convertible into or exchangeable for the shares of our Common Stock in the course of hedging positions they assume with the selling shareholders and may deliver such securities to close out their short positions or otherwise settle short sales or other transactions. The selling shareholders may also loan or pledge shares to broker-dealers or other third parties. In connection with those transactions, the broker-dealers or other third parties may sell such loaned or pledged shares. The selling shareholders may also enter into options or other transactions with broker-dealers or other financial institutions which require the delivery of shares offered by this prospectus to those broker-dealers or other financial institutions. The broker-dealer or other financial institution may then resell the shares pursuant to this prospectus (as amended or supplemented, if required by applicable law, to reflect those transactions).

The selling shareholders and any broker-dealers that act in connection with the sale of shares may be deemed to be “underwriters” within the meaning of Section 2(a)(11) of the Securities Act of 1933, and any commissions received by broker-dealers or any profit on the resale of the shares sold by them while acting as principals may be deemed to be underwriting discounts or commissions under the Securities Act. The selling shareholders may agree to indemnify any agent, dealer or broker-dealer that participates in transactions involving sales of the shares against liabilities, including liabilities arising under the Securities Act. We have agreed to indemnify each of the selling shareholders and each selling shareholder has agreed to indemnify us against certain liabilities in connection with the offering of the shares, including liabilities arising under the Securities Act.

The selling shareholders will be subject to the prospectus delivery requirements of the Securities Act. We have informed the selling shareholders that the anti-manipulative provisions of Regulation M promulgated under the Securities Exchange Act of 1934 may apply to their sales in the market.

Selling shareholders also may resell all or a portion of the shares in open market transactions in reliance upon Rule 144 under the Securities Act, provided they meet the criteria and conform to the requirements of Rule 144.

We are paying all expenses and fees in connection with the registration of the shares. The selling shareholders will bear all brokerage or underwriting discounts or commissions paid to broker-dealers in connection with the sale of the shares.

Wells Fargo Bank Minnesota, N.A., located at P.O. Box 64854, St. Paul, MN 55164-0854, is the transfer agent and registrar for our Common Stock.

LEGAL MATTERS

The validity of the shares offered by this prospectus has been passed upon by Browne Rosedale & Lanouette LLP.

EXPERTS

The consolidated balance sheet of Sontra Medical Corporation and Subsidiary as of December 31, 2002, and the related consolidated statements of loss, convertible preferred stock and stockholders’ equity and cash flows for the year then ended and for the cumulative period from inception (January 29, 1996) to December 31, 2002, except for the period from inception

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(January 29, 1996) to December 31, 2001 which was audited by other auditors who have ceased operations, have been incorporated by reference herein and in the registration statement in reliance upon the report of Wolf & Company, P.C., independent auditors, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The balance sheets of Sontra Medical, Inc. (a Delaware corporation in the development stage) as of December 31, 2000 and 2001 and the related statements of operations, convertible preferred stock and stockholders’ deficit and cash flows for each of the three years in the period ended December 31, 2001 and for the cumulative period from inception (January 29, 1996) to December 31, 2001, have been incorporated by reference herein and in the registration statement in reliance upon the report of Arthur Andersen LLP, independent accountants, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

Arthur Andersen LLP has not consented to the inclusion of their report in this prospectus, and we have not obtained their consent to do so in reliance upon Rule 437a of the Securities Act. The absence of this consent may limit recovery against Arthur Andersen LLP under Section 11 of the Securities Act for any untrue statement of a material fact, or any omission to state a material fact required to be stated, in the financial statements audited by Arthur Andersen LLP. Also, as a practical matter, Arthur Andersen LLP’s ability to satisfy any claims may be limited due to events arising out of their conviction on federal obstruction of justice charges.

INDEMNIFICATION OF DIRECTORS AND OFFICERS

Section 302A.521 of the Minnesota Business Corporation Act provides that unless prohibited or limited by a corporation’s articles of incorporation or bylaws, a corporation shall indemnify any person made or threatened to be made a party to a proceeding by reason of the former or present official capacity of such person against judgments, penalties, fines, including, without limitation, excise taxes assessed against such person with respect to an employee benefit plan, settlements and reasonable expenses, including attorneys’ fees and disbursements, incurred by such person in connection with the proceeding, if, with respect to the acts or omissions of such person complained of in the proceeding, such person: (1) has not been indemnified therefor by another organization or employee benefit plan; (2) acted in good faith; (3) received no improper personal benefit and Section 302A.255 (with respect to director conflicts of interest), if applicable, has been satisfied; (4) in the case of a criminal proceeding, had no reasonable cause to believe the conduct was unlawful; and (5) reasonably believed that the conduct was in the best interests of the corporation in the case of acts or omissions in such person’s official capacity for the corporation, or reasonably believed that the conduct was not opposed to the best interests of the corporation in the case of acts or omissions in such person’s official capacity for other affiliated organizations. Section 302A.521 also permits a corporation to purchase and maintain insurance on behalf of its officers, directors, employees and agents against any liability which may be asserted against, or incurred by, such persons in their capacities as officers, directors, employees and agents of the corporation, whether or not the corporation would have been required to indemnify the person against the liability under the provisions of such section.

Article 7 of our Second Amended and Restated Articles of Incorporation eliminates the personal liability of directors to the Company or its stockholders for monetary damages for breaches of their fiduciary duty to the fullest extent permitted by the Minnesota Business Corporation Act.

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Article 7 of our Amended and Restated Bylaws provides that directors and officers and certain other persons shall have the rights to indemnification provided by Section 302A.521 of the Minnesota Business Corporation Act. Article 7 also provides that the Company shall have the power to purchase and maintain insurance on behalf of a person in that person’s official capacity against any liability asserted against and incurred by the person in or arising from that capacity.

We maintain an insurance policy on behalf of the Company and our directors and officers, covering certain liabilities which may arise as a result of the actions of the directors and officers, including liabilities that may arise under the Securities Act of 1933, as amended.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Company pursuant to the foregoing provisions, or otherwise, the Company has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

The following table sets forth the various expenses to be incurred in connection with the sale and distribution of the securities being registered hereby, all of which will be borne by Sontra Medical Corporation (except any underwriting discounts and commissions and expenses incurred by the selling shareholders for brokerage, accounting, tax or legal services or any other expenses incurred by the selling shareholders in disposing of the shares). All amounts shown are estimates except the Securities and Exchange Commission registration fee.

Filing Fee—Securities and Exchange Commission	$	3,473.14
Legal fees and expenses	$	15,000
Accounting fees and expenses	$	2,500
Miscellaneous expenses	$	2,026.86
Total Expenses	$	23,000

Item 15. Indemnification of Directors and Officers.

Section 302A.521 of the Minnesota Business Corporation Act provides that unless prohibited or limited by a corporation’s articles of incorporation or bylaws, a corporation shall indemnify any person made or threatened to be made a party to a proceeding by reason of the former or present official capacity of such person against judgments, penalties, fines, including, without limitation, excise taxes assessed against such person with respect to an employee benefit plan, settlements and reasonable expenses, including attorneys’ fees and disbursements, incurred by such person in connection with the proceeding, if, with respect to the acts or omissions of such person complained of in the proceeding, such person: (1) has not been indemnified therefor by another organization or employee benefit plan; (2) acted in good faith; (3) received no improper personal benefit and Section 302A.255 (with respect to director conflicts of interest), if applicable, has been satisfied; (4) in the case of a criminal proceeding, had no reasonable cause to believe the conduct was unlawful; and (5) reasonably believed that the conduct was in the best interests of the corporation in the case of acts or omissions in such person’s official capacity for the corporation, or reasonably believed that the conduct was not opposed to the best interests of the corporation in the case of acts or omissions in such person’s official capacity for other affiliated organizations. Section 302A.521 also permits a corporation to purchase and maintain insurance on behalf of its officers, directors, employees and agents against any liability which may be asserted against, or incurred by, such persons in their capacities as officers, directors, employees and agents of the corporation, whether or not the corporation would have been required to indemnify the person against the liability under the provisions of such section.

Article 7 of the Registrant’s Second Amended and Restated Articles of Incorporation eliminates the personal liability of directors to the Registrant or its stockholders for monetary damages for breaches of their fiduciary duty to the fullest extent permitted by the Minnesota Business Corporation Act.

Article 7 of the Registrant’s Amended and Restated Bylaws provides that directors and officers and certain other persons shall have the rights to indemnification provided by Section

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302A.521 of the Minnesota Business Corporation Act. Article 7 also provides that the Registrant shall have the power to purchase and maintain insurance on behalf of a person in that person’s official capacity against any liability asserted against and incurred by the person in or arising from that capacity.

The Registrant maintains an insurance policy on behalf of itself and its directors and officers, covering certain liabilities which may arise as a result of the actions of the directors and officers.

Item 16. Exhibits.

Exhibit Number	Description
4.1	Specimen Certificate of Common Stock, $.01 par value per share, of the Registrant is incorporated herein by reference to Exhibit 4.02 to the Registrant’s Annual Report on Form 10-KSB for the fiscal year ended December 31, 2002 (File No. 000-23017).
4.2	Statement of the Powers, Designations, Preferences and Rights of the Series A Convertible Preferred Stock of the Registrant.
5	Opinion of Browne Rosedale & Lanouette LLP.
23.1	Consent of Browne Rosedale & Lanouette LLP (included in Exhibit 5).
23.2	Consent of Wolf & Company, P.C.
23.3*	Consent of Arthur Andersen LLP (omitted pursuant to Rule 437(a)).
24	Power of Attorney (included in the signature pages of this Registration Statement).
99.1	Form of Subscription Agreement is incorporated herein by reference to Appendix C to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.2	Form of Series A Unit Supplemental Agreement is incorporated herein by reference to Appendix F to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.3	Form of Common Stock Purchase Warrant is incorporated herein by reference to Appendix E to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.4	Form of Placement Agent Common Stock Purchase Warrant.

* After reasonable efforts, the Registrant has not been able to obtain the consent of Arthur Andersen LLP to the incorporation into this Registration Statement on Form S-3 of its report with respect to the Registrant’s financial statements, which appeared in the Registrant’s Annual Report on Form 10-KSB for the year ended December 31, 2002. Under these circumstances, Rule 437(a) under the Securities Act of 1933, as amended, permits this Registration Statement to be filed without a written consent from Arthur Andersen LLP. Because Arthur Andersen LLP has not

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consented to the incorporation by reference of their report into this Registration Statement, you will not be able to assert claims against Arthur Andersen LLP under Section 11 of the Securities Act of 1933, as amended, for any untrue statement of a material fact contained in the Registrant’s financial statements incorporated herein or any omissions to state a material fact required to be stated therein.

Item 17. Undertakings.

The undersigned Registrant hereby undertakes:

(1) To file, during any period in which it offers or sells securities, a post-effective amendment to this registration statement to include any additional or changed material information on the plan of distribution.

(2) For determining liability under the Securities Act, to treat each post-effective amendment as a new registration statement of the securities offered, and the offering of the securities at that time to be the initial bona fide offering.

(3) To file a post-effective amendment to remove from registration any of the securities that remain unsold at the end of the offering.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the small business issuer pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the small business issuer in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the Town of Franklin, Commonwealth of Massachusetts on October 15, 2003.

SONTRA MEDICAL CORPORATION
By:	/s/ Thomas W. Davison
	Thomas W. Davison
	President and Chief Executive Officer

POWER OF ATTORNEY

We, the undersigned officers and directors of Sontra Medical Corporation, hereby severally constitute and appoint Thomas W. Davison and Sean F. Moran, and each of them singly, our true and lawful attorneys with full power to them, and each of them singly, to sign for us and in our names in the capacities indicated below, the Registration Statement on Form S-3 filed herewith and any and all pre-effective and post-effective amendments to said Registration Statement and generally to do all such things in our name and behalf in our capacities as officers and directors to enable Sontra Medical Corporation to comply with the provisions of the Securities Act of 1933, as amended, and all requirements of the Securities and Exchange Commission, hereby ratifying and confirming our signatures as they may be signed by our said attorneys, or any of them, to said Registration Statement and any and all amendments thereto.

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Pursuant to the requirements of the Securities Act, this Registration Statement has been signed by the following persons in the capacities indicated on October 15, 2003.

Signature	Title
/s/ James R. McNab, Jr. James R. McNab, Jr.	Chairman of the Board of Directors
/s/ Thomas W. Davison Thomas W. Davison	President, Chief Executive Officer and Director (Principal Executive Officer)
/s/ Sean F. Moran Sean F. Moran	Chief Financial Officer (Principal Financial and Accounting Officer)
/s/ Joseph Amaral Joseph Amaral	Director
Gary S. Kohler	Director
/s/ Robert S. Langer Robert S. Langer	Director
/s/ Martin P. Sutter Martin P. Sutter	Director
/s/ W. Leigh Thompson W. Leigh Thompson	Director
/s/ Michael Wigley Michael Wigley	Director

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EXHIBIT INDEX

Exhibit Number	Description
4.1	Specimen Certificate of Common Stock, $.01 par value per share, of the Registrant is incorporated herein by reference to Exhibit 4.02 to the Registrant’s Annual Report on Form 10-KSB for the fiscal year ended December 31, 2002 (File No. 000-23017).
4.2	Statement of the Powers, Designations, Preferences and Rights of the Series A Convertible Preferred Stock of the Registrant.
5	Opinion of Browne Rosedale & Lanouette LLP.
23.1	Consent of Browne Rosedale & Lanouette LLP (included in Exhibit 5).
23.2	Consent of Wolf & Company, P.C.
23.3*	Consent of Arthur Andersen LLP (omitted pursuant to Rule 437(a)).
24	Power of Attorney (included in the signature pages of this Registration Statement).
99.1	Form of Subscription Agreement is incorporated herein by reference to Appendix C to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.2	Form of Series A Unit Supplemental Agreement is incorporated herein by reference to Appendix F to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.3	Form of Common Stock Purchase Warrant is incorporated herein by reference to Appendix E to the Registrant’s Definitive Schedule 14A filed September 8, 2003 (File No. 000-23017).
99.4	Form of Placement Agent Common Stock Purchase Warrant.

* After reasonable efforts, the Registrant has not been able to obtain the consent of Arthur Andersen LLP to the incorporation into this Registration Statement on Form S-3 of its report with respect to the Registrant’s financial statements, which appeared in the Registrant’s Annual Report on Form 10-KSB for the year ended December 31, 2002. Under these circumstances, Rule 437(a) under the Securities Act of 1933, as amended, permits this Registration Statement to be filed without a written consent from Arthur Andersen LLP. Because Arthur Andersen LLP has not consented to the incorporation by reference of their report into this Registration Statement, you will not be able to assert claims against Arthur Andersen LLP under Section 11 of the Securities Act of 1933, as amended, for any untrue statement of a material fact contained in the Registrant’s financial statements incorporated herein or any omissions to state a material fact required to be stated therein.

EX-4.2

EXHIBIT 4.2

STATEMENT OF THE POWERS, DESIGNATIONS, PREFERENCES AND

RIGHTS OF THE SERIES A CONVERTIBLE PREFERRED STOCK,

PAR VALUE $0.01 PER SHARE

OF

SONTRA MEDICAL CORPORATION

Sontra Medical Corporation, a Minnesota corporation (the “Corporation”), does hereby certify, pursuant to Chapter 302A.401 of the Minnesota Business Corporations Act, that the following resolution, creating a series of seven million (7,000,000) shares of Series A Preferred Stock, was duly adopted by the Board of Directors on September 8, 2003.

RESOLVED, that pursuant to the authority granted to and vested in the Board of Directors in accordance with the provisions of the Amended and Restated Articles of Incorporation of the Corporation, as amended, there shall be created a series of Preferred Stock, $0.01 par value, which series shall have the following designations and number thereof, powers, preferences, rights, qualifications, limitations and restrictions:

1. Designation and Number of Shares. There shall be hereby created and established a series of Preferred Stock designated as “Series A Convertible Preferred Stock” (the “Series A Preferred Stock”). The authorized number of shares of Series A Preferred Stock shall be seven million (7,000,000). The stated value is $1.00 per share of Series A Preferred Stock (the “Stated Value Per Share”). Capitalized terms used herein and not otherwise defined shall have the meanings set forth in Section 8 below.

2. Rank. The Series A Preferred Stock shall with respect to (i) the payment of the Liquidation Payment in the event of Liquidation, (ii) the payment of the Sale Payment in the event of a Change of Control and (iii) the payment of dividends rank senior to all classes of common stock of the Corporation (including, without limitation, the Common Stock) and each other class or series of Capital Stock of the Corporation hereafter created which does not expressly rank pari passu with or senior to the Series A Preferred Stock (together, the “Junior Stock”).

3. Dividends.

(a) Dividend Rate. The holders of shares of Series A Preferred Stock shall be entitled to cumulative dividends annually (except as set forth below) in arrears on June 30 of each year at an annual rate equal to eight percent (8.0%) of the Stated Value Per Share, calculated on the basis of a 360-day year, consisting of twelve (12) thirty (30)-day months, which shall accrue on a daily basis from the date of issuance thereof, whether or not declared by the Board of Directors. Dividends shall be payable in cash or Common Stock at the Corporation’s discretion. If a full or partial dividend on the shares of Series A Preferred Stock with respect to any year is not declared by the Board of Directors, the Corporation shall remain obligated to pay a full dividend with respect to that year; provided, however, that any unpaid dividends shall not bear interest. Each

record date declared by the Board of Directors for the payment of dividends pursuant to this Section 3(a) is sometimes referred to herein as the “Compounding Date”. At the election of the Corporation, each dividend on the Series A Preferred Stock may be added to the Accreted Value. In the event that the Corporation elects to pay dividends on the Series A Preferred Stock in shares of Common Stock in accordance with this Section 3(a), the shares of Common Stock to be delivered to the holders of the Series A Preferred Stock shall be valued at their Current Market Price as of the record date declared by the Board of Directors.

(b) Other Dividends. The Corporation shall not declare or pay any dividends on, or make any other distributions with respect to any other shares of Capital Stock unless and until all accrued dividends on the Series A Preferred Stock have been paid in full.

(c) Common Stock Dividends. If the Corporation declares and pays any dividends on the Common Stock, then, in that event, holders of shares of Series A Preferred Stock shall be entitled to share in such dividends on a pro rata basis, as if their shares have been converted into shares of Common Stock pursuant to Section 6(a) below immediately prior to the record date for determining the shareholders of the Corporation eligible to receive such dividends.

4. Liquidation and Change of Control.

(a) Priority Payment. Upon the occurrence of and simultaneously with a Liquidation, the holders of shares of Series A Preferred Stock shall be paid in cash for each share of Series A Preferred Stock held thereby, out of, but only to the extent of, the assets of the Corporation legally available for distribution to its shareholders, before any payment or distribution is made to any Junior Stock, an amount equal to the sum of (x) the Accreted Value of such share of Series A Preferred Stock on the date of such Liquidation plus (y) all unpaid dividends accrued at the rate and in the manner specified in Section 3(a) since the previous Compounding Date to the date of Liquidation (the “Liquidation Payment”). If the assets of the Corporation available for distribution to the holders of shares of Series A Preferred Stock shall be insufficient to permit payment in full to such holders of the aggregate Liquidation Payment, then all of the assets available for distribution to holders of shares of Series A Preferred Stock shall be distributed among and paid to such holders ratably in proportion to the amounts that would be payable to such holders if such assets were sufficient to permit payment in full.

(b) Change of Control. In the event of a Change of Control, the holders of shares of Series A Preferred Stock shall be paid for each share of Series A Preferred Stock held thereby, before any payment or distribution is made to any Junior Stock, a cash amount equal to (i) the sum of (x) the Accreted Value of such share of Series A Preferred Stock on the closing date of such Change of Control plus (y) all unpaid dividends accrued at the rate and in the manner specified in Section 3(a) since the previous Compounding Date to the closing date of such Change of Control (the “Sale Payment”). If the assets of the Corporation available for distribution to the holders of shares of Series A Preferred Stock shall be insufficient to permit payment in full to such holders of the aggregate Sale Payment, then all of the assets available for distribution to

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holders of shares of Series A Preferred Stock shall be distributed among and paid to such holders ratably in proportion to the amounts that would be payable to such holders if such assets were sufficient to permit payment in full. Any amount payable under this Section 4(b) shall be paid on the closing date of such Change of Control.

(c) No Additional Payment. After the holders of all shares of Series A Preferred Stock shall have been paid in full the amounts to which they are entitled in Section 4(a) or Section 4(b), as the case may be, the holders of shares of Series A Preferred Stock shall not be entitled to any further participation in any distribution of assets of the Corporation and the remaining assets of the Corporation shall be distributed to the holders of Junior Stock.

(d) Notice. Written notice of a Liquidation or a Change of Control stating a payment or payments and the place where such payment or payments shall be payable, shall be delivered in person, mailed by certified mail, return receipt requested, mailed by overnight mail or sent by telecopier, not less than ten (10) days prior to the date on which such Liquidation or Change of Control is expected to become effective, to the holders of record of shares of Series A Preferred Stock, such notice to be addressed to each such holder at its address as shown by the records of the Corporation.

5. Voting Rights. Unless and until the shares of Series A Preferred Stock are converted into Common Stock in accordance with Section 6(a) or (b) below, the holders of outstanding shares of Series A Preferred Stock shall not be entitled to vote on any matters except to the extent otherwise required under the Minnesota Business Corporations Act.

6. Conversion and Redemption.

(a) Conversion at Option of Holder. Any holder of shares of Series A Preferred Stock shall have the right, at its option, at any time and from time to time, to convert, subject to the terms and provisions of this Section 6 (other than 6(b)), any or all of such holder’s shares of Series A Preferred Stock into such number of fully paid and non-assessable shares of Common Stock as is equal to the product of (i) the number of shares of Series A Preferred Stock being so converted multiplied by (ii) the quotient of (x) the sum of the Accreted Value plus all unpaid dividends accrued at the rate and in the manner specified in Section 3(a) since the previous Compounding Date divided by (y) the Per Share Price, subject to adjustment as provided in Section 6(e) below (the “Conversion Price”) (such quotient being sometimes referred to herein as the “Conversion Ratio”). Such conversion right shall be exercised by the surrender of certificate(s) representing the shares of Series A Preferred Stock to be converted to the Corporation at any time during usual business hours at its principal place of business maintained by it (or such other office or agency of the Corporation as the Corporation may designate by notice in writing to the holders of shares of Series A Preferred Stock), accompanied by written notice that the holder elects to convert such shares of Series A Preferred Stock and specifying the name or names (with address) in which a certificate or certificates for shares of Common Stock are to be issued and (if so required by the Corporation) by a written instrument or instruments of transfer in form reasonably satisfactory to the Corporation duly executed by the holder or its duly authorized legal

3

representative and transfer tax stamps or funds therefor, if required pursuant to Section 6(k) below. Notwithstanding anything herein to the contrary, the Series A Preferred Stock shall not be convertible unless and until the Corporation’s shareholders approve, as required by Nasdaq Marketplace Rule 4350, the issuance of the shares of Common Stock upon conversion of the Series A Preferred Stock (the “Nasdaq Approval”).

(b) Conversion at Option of the Corporation. If, on any date after the effectiveness of the Registration Statement (as defined in Subscription Agreements by and between the Corporation and each of the holders of the Series A Preferred Stock (the “Subscription Agreements”)), the closing Market Price for a share of Common Stock for twenty (20) consecutive trading days equals at least $3.00 (subject to adjustment for the events described in Section 6(e)(i)), the Corporation shall have the right, at its option, to convert, subject to the terms and provisions of this Section 6, all, but not less than all, of the outstanding shares of Series A Preferred Stock into such number of fully paid and non-assessable shares of Common Stock as is equal to the product of (i) the number of shares of Series A Preferred Stock being so converted multiplied by (ii) the Conversion Ratio. Written notice by the Corporation that the Corporation elects to convert such shares of Series A Preferred Stock pursuant to this Section 6(b) shall be delivered in person, mailed by certified mail, return receipt requested, mailed by overnight mail or sent by telecopier to the holders of record of the shares of Series A Preferred Stock, such notice to set forth the date of conversion pursuant to this Section 6(b) and to be addressed to each such holder at its address as shown in the records of the Corporation. Upon receipt of such notice from the Corporation, each holder of shares of Series A Preferred Stock shall promptly surrender to the Corporation certificates representing the shares of Series A Preferred Stock to be converted at any time during usual business hours at its principal place of business maintained by it (or such other office or agency of the Corporation as the Corporation may designate by notice in writing to the holders of shares of Series A Preferred Stock), specifying the name or names (with address) in which a certificate or certificates for shares of Common Stock are to be issued and (if so required by the Corporation) accompanied by a written instrument or instruments of transfer in form reasonably satisfactory to the Corporation duly executed by the holder or its duly authorized legal representative and transfer tax stamps or funds therefore, if required pursuant to Section 6(k) below. Notwithstanding anything herein to the contrary, the Series A Preferred Stock shall not be convertible unless and until the Nasdaq Approval is obtained.

(c) Surrender of Certificates; Delivery of Shares; Termination of Rights. All certificates representing shares of Series A Preferred Stock surrendered for conversion pursuant to Sections 6(a) and 6(b) shall be delivered to the Corporation for cancellation and canceled by it. As promptly as practicable after the surrender of any shares of Series A Preferred Stock, the Corporation shall (subject to compliance with the applicable provisions of federal and state securities laws) deliver to the holder of such shares so surrendered certificate(s) representing the number of fully paid and nonassessable shares of Common Stock into which such shares are entitled to be converted. At the time of the surrender of such certificate(s), the Person in whose name any certificate(s) for shares of Common Stock shall be issuable upon such conversion

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shall be deemed to be the holder of record of such shares of Common Stock on such date, notwithstanding that the share register of the Corporation shall then be closed or that the certificates representing such Common Stock shall not then be actually delivered to such Person. Such converted Series A Preferred Stock may not be reissued, and the Corporation may thereafter take such appropriate action (without the need for stockholder action) as may be necessary to reduce the authorized number of shares of Series A Preferred Stock accordingly. On the date of conversion pursuant to Section 6(a) or Section 6(b) above, all rights with respect to the shares of Series A Preferred Stock so converted, including the rights, if any, to receive notices and vote, shall terminate, except only the rights of holders thereof to (i) receive certificates for the number of shares of Common Stock into which such shares of Series A Preferred Stock have been converted and (ii) exercise the rights to which they are entitled as holders of Common Stock.

(d) Adjustments to Per Share Price. (i) In the event the Corporation shall at any time after the Closing Date and prior to the later to occur of (1) the first anniversary of the Closing Date, (2) the date that is 90 days after the effectiveness of the Registration Statement or (3) the date that the closing Market Price for a share of Common Stock for thirty (30) consecutive trading days is at least equal to the Conversion Price, issue Additional Shares of Common Stock for a consideration per share less than the Conversion Price in effect on the date of and immediately prior to such issue, then and in such event, such Conversion Price shall be reduced, concurrently with such issue, to the consideration per share received by the Corporation for the issue of the Additional Shares of Common Stock. For the purpose of the adjustment required under this Section 6(d), if the Corporation issues or sells any Convertible Securities or Options for a consideration per share less than the Conversion Price in effect on the date of and immediately prior to such issue, in each case the Corporation shall be deemed to have issued at the time of such issuance, the maximum number of Additional Shares of Common Stock issuable upon exercise or conversion thereof and to have received as consideration for the issuance of such shares an amount equal to the total amount of the consideration, if any, received by the Corporation for the issuance of such Convertible Securities or Options, plus, in the case of such Options, the minimum amounts of consideration, if any, payable to the Corporation upon the exercise of such Options, plus, in the case of Convertible Securities, the minimum amounts of consideration, if any, payable to the Corporation (other than by cancellation of liabilities or obligations evidenced by such Convertible Securities) upon the conversion thereof. All calculations of the above amounts shall be made without regard to any limitation on conversions or exercises of such Convertible Securities or Options.

For purposes of this Statement:

“Convertible Securities” shall mean any evidence of indebtedness, shares or other securities directly or indirectly convertible into or exchangeable for Common Stock, but excluding Options.

“Option” shall mean rights, options or warrants to subscribe for, purchase or otherwise acquire Common Stock or Convertible Securities.

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“Additional Shares of Common Stock” shall mean all shares of Common Stock, Convertible Securities and all Options issued (or deemed to be issued pursuant to this Section 6(d)(i)) by the Corporation after the Closing Date, other than:

(1) shares of Common Stock issued or issuable upon conversion or exchange of any Convertible Securities or exercise of any Options outstanding on the Closing Date; provided that adjustment for the issuance of such Convertible Securities and Options has previously been made (for such Convertible Securities and Options issued after the Closing Date);

(2) shares of Common Stock issued or issuable as a dividend or distribution on Series A Preferred Stock;

(3) shares of Common Stock issued or issuable by reason of a dividend, stock split or other distribution on shares of Common Stock that is covered by Section 6(e) below;

(4) shares of Common Stock issued or issuable in connection with the offering and issuance of the Series A Preferred Stock pursuant to the Subscription Agreements; or

(5) shares of Common Stock (or Options with respect thereto) issued or issuable to employees or directors of, or consultants to, the Corporation pursuant to a plan or arrangement approved by the Board of Directors of the Corporation.

(ii) In the event that (1) the Corporation has not filed the Registration Statement with the Commission within 30 days after the Closing Date, or (2) the Registration Statement has not been declared effective by the Commission within 120 days after the Closing Date, then the Per Share Price then in effect shall be adjusted such that the number of shares of Common Stock issuable upon conversion of the shares of Series A Preferred Stock shall be increased by 1% for each full 30-day period during which both of the above-stated conditions are not met.

(e) (i) Dividend, Subdivision, Combination or Reclassification of Common Stock. In the event that the Corporation shall, at any time or from time to time prior to conversion of shares of Series A Preferred Stock, (w) declare a dividend or make a distribution on the outstanding shares of Common Stock payable in Common Stock, (x) subdivide the outstanding shares of Common Stock into a larger number of shares, (y) combine the outstanding shares of Common Stock into a smaller number of shares or (z) issue any shares of its Capital Stock in a reclassification of the Common Stock (other than any such event for which an adjustment is made pursuant to another clause of this Section 6(e)), then, and in each such case, the Conversion Price in effect immediately prior to such event shall be adjusted (and any other appropriate actions shall be taken by the Corporation) so that the holder of any share of Series A Preferred Stock thereafter surrendered for conversion shall be entitled to receive the number of shares of Common Stock or other securities of the Corporation that such holder would have owned or would have been entitled to receive upon or by reason of

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any of the events described above, had such share of Series A Preferred Stock been converted immediately prior to the occurrence of such event. An adjustment made pursuant to this Section 6(e)(i) shall become effective retroactively (x) in the case of any such dividend or distribution, to a date immediately following the close of business on the record date for the determination of holders of Common Stock entitled to receive such dividend or distribution or (y) in the case of any such subdivision, combination or reclassification, to the close of business on the day upon which such corporate action becomes effective.

(ii) Certain Distributions. In case the Corporation shall, at any time or from time to time prior to conversion of shares of Series A Preferred Stock, distribute to all holders of shares of the Common Stock (including any such distribution made in connection with a merger or consolidation in which the Corporation is the resulting or surviving Person and the Common Stock is not changed or exchanged) cash, evidences of Indebtedness of the Corporation or another issuer, securities of the Corporation or another issuer or other assets (excluding dividends payable in shares of Common Stock for which adjustment is made under another paragraph of this Section 6(e), any distribution that also is made to the holders of Series A Preferred Stock on an as-converted basis and any distribution in connection with an Excluded Transaction) or rights or warrants to subscribe for or purchase of any of the foregoing, then, and in each such case, the Conversion Price then in effect shall be adjusted (and any other appropriate actions shall be taken by the Corporation) by multiplying the Conversion Price in effect immediately prior to the date of such distribution by a fraction (x) the numerator of which shall be the Current Market Price of the Common Stock immediately prior to the date of distribution less the then fair market value (as determined by the Board of Directors in the exercise of their fiduciary duties) of the portion of the cash, evidences of Indebtedness, securities or other assets so distributed or of such rights or warrants applicable to one share of Common Stock and (y) the denominator of which shall be the Current Market Price of the Common Stock immediately prior to the date of distribution (but such fraction shall not be greater than one); provided, however, that no adjustment shall be made with respect to any distribution of rights or warrants to subscribe for or purchase securities of the Corporation if the holder of shares of Series A Preferred Stock would otherwise be entitled to receive such rights or warrants upon conversion at any time of shares of Series A Preferred Stock into Common Stock. Such adjustment shall be made whenever any such distribution is made and shall become effective retroactively to a date immediately following the close of business on the record date for the determination of shareholders entitled to receive such distribution.

(iii) Other Changes. In case the Corporation, at any time or from time to time prior to the conversion of shares of Series A Preferred Stock, shall take any action affecting its Common Stock similar to or having an effect similar to any of the actions described in Sections 6(e)(i) or (ii) above or Section 6(h) below (but not including any action described in any such Section) and the Board of Directors in good faith determines that it would be equitable in the circumstances to adjust the Conversion Price as a result of such action, then, and in each such case, the Conversion Price shall be adjusted in such manner and at such time as the Board of Directors in good faith determines would be equitable in the circumstances (such determination to be

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evidenced in a resolution, a certified copy of which shall be mailed to the holders of shares of Series A Preferred Stock).

(f) Abandonment. If the Corporation shall take a record of the holders of its Common Stock for the purpose of entitling them to receive a dividend or other distribution, and shall thereafter and before the distribution to shareholders thereof legally abandon its plan to pay or deliver such dividend or distribution, then no adjustment in the Conversion Price shall be required by reason of the taking of such record.

(g) Certificate as to Adjustments. Upon any adjustment in the Conversion Price, the Corporation shall within five (5) business days following any of the foregoing transactions deliver to each registered holder of shares of Series A Preferred Stock a certificate, signed by an appropriate officer of the Corporation, setting forth in reasonable detail the event requiring the adjustment and the method by which such adjustment was calculated and specifying the increased or decreased Conversion Price then in effect following such adjustment.

(h) Reorganization, Reclassification. In case of any merger, consolidation or other business combination transaction of the Corporation (other than a Change of Control) or any capital reorganization, reclassification or other change of outstanding shares of Common Stock (other than a change in par value, or from par value to no par value, or from no par value to par value) (each, a “Transaction”), the Corporation shall execute and deliver to each holder of shares of Series A Preferred Stock prior to effecting such Transaction a certificate, signed by an appropriate officer of the Corporation, stating that the holder of each share of Series A Preferred Stock shall have the right to receive in such Transaction, in exchange for each share of Series A Preferred Stock, a security identical to (and not less favorable than) the Series A Preferred Stock, and provision shall be made therefor in the agreement, if any, relating to such Transaction. Any certificate delivered pursuant to this Section 6(h) shall provide for adjustments which shall be as nearly equivalent as may be practicable to the adjustments provided for in this Section 6. The provisions of this Section 6(h) and any equivalent thereof in any such certificate similarly shall apply to successive Transactions.

(i) Notices. In case at any time or from time to time:

(w) the Corporation shall declare a dividend (or any other distribution) on its shares of Common Stock;

(x) the Corporation subdivides or combines its outstanding shares of Common Stock;

(y) the Corporation shall authorize the granting to the holders of its Common Stock rights or warrants to subscribe for or purchase any shares of Capital Stock of any class or of any other rights or warrants; or

(z) there shall be any Transaction,

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then the Corporation shall mail to each holder of shares of Series A Preferred Stock at such holder’s address as it appears on the transfer books of the Corporation, as promptly as practicable but in any event at least ten days prior to the applicable date hereinafter specified, a notice stating (A) the date on which a record is to be taken for the purpose of such dividend, distribution, subdivision, combination or granting of rights or warrants or, if a record is not to be taken, the date as of which the holders of Common Stock of record to be entitled to such dividend, distribution, subdivision, combination or granting of rights or warrants are to be determined, or (B) the date on which such Transaction is expected to become effective and the date as of which it is expected that holders of Common Stock of record shall be entitled to exchange their Common Stock for shares of stock or other securities or property or cash deliverable upon such Transaction. Notwithstanding the foregoing, in the case of any event to which Section 6(h) above is applicable, the Corporation shall also deliver the certificate described in Section 6(h) above to each holder of shares of Series A Preferred Stock prior to effecting such reorganization or reclassification as aforesaid.

(j) Listing. The Corporation shall: (i) prepare and file with The Nasdaq Stock Market on a timely basis the necessary Notification Form regarding the listing on the Nasdaq SmallCap Market (“NSCM”) of a number of additional shares of Common Stock which is at least equal to the maximum number of shares then issuable upon conversion of the Series A Preferred Stock (without regard to any limitation on conversions of Series A Preferred Stock); (ii) maintain, so long as any other shares of Common Stock shall be so listed, the listing of all such shares then issuable upon conversion of the Series A Preferred Stock on the NSCM; and (iii) provide to the Subscriber evidence of such filing upon request.

(k) Reservation of Common Stock. The Corporation shall at all times reserve and keep available for issuance upon the conversion of shares of Series A Preferred Stock, such number of its authorized but unissued shares of Common Stock as will from time to time be sufficient to permit the conversion of all outstanding shares of Series A Preferred Stock, and shall take all action to increase the authorized number of shares of Common Stock if at any time there shall be insufficient authorized but unissued shares of Common Stock to permit such reservation or to permit the conversion of all outstanding shares of Series A Preferred Stock; provided, that the holders of shares of Series A Preferred Stock shall vote such shares in favor of any such action that requires a vote of shareholders.

(l) No Conversion Tax or Charge. The issuance or delivery of certificates for Common Stock upon the conversion of shares of Series A Preferred Stock shall be made without charge to the converting holder of shares of Series A Preferred Stock for such certificates or for any tax in respect of the issuance or delivery of such certificates or the securities represented thereby, and such certificates shall be issued or delivered in the respective names of, or (subject to compliance with the applicable provisions of federal and state securities laws) in such names as may be directed by, the holders of the shares of Series A Preferred Stock so converted; provided, however, that the Corporation shall not be required to pay any tax which may be payable in respect of any transfer involved in the issuance and delivery of any such certificate in a name other than that of the holder of the shares of Series A Preferred Stock so converted, and the

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Corporation shall not be required to issue or deliver such certificate unless or until the Person or Persons requesting the issuance or delivery thereof shall have paid to the Corporation the amount of such tax or shall have established to the reasonable satisfaction of the Corporation that such tax has been paid.

(m) Limitations on Conversions. Each holder of the Series A Preferred Stock’s right to convert its shares of Series A Preferred Stock into shares of Common Stock shall not be limited by any notice delivered by the Corporation of any Change of Control or other event that notwithstanding this subsection (l) shall purport to limit such conversion right.

(n) No Fractional Shares. No fractional shares of Common Stock shall be issued upon conversion of the Series A Preferred Stock. In lieu of any fractional shares to which the holder would otherwise be entitled, the Corporation shall pay cash equal to such fraction multiplied by the Market Price on the trading day immediately preceding conversion.

(o) Redemption. At any time after the fifth anniversary of the Closing Date, the Corporation shall have the right to redeem the shares of Series A Preferred Stock at a per share price equal to the Stated Value Per Share, subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization affecting the number of issued and outstanding shares of Series A Preferred Stock, plus any accrued and unpaid dividends. Shares of the Series A Preferred Stock redeemed or otherwise repurchased or reacquired by the Corporation shall be restored to the status of authorized but unissued shares of Preferred Stock, without designation as to series, and may thereafter be issued, but not as shares of the Series A Preferred Stock.

7. Business Day. If any payment shall be required by the terms hereof to be made on a day that is not a Business Day, such payment shall be made on the immediately succeeding Business Day.

8. Definitions. As used in this Statement of Designations, the following terms shall have the following meanings (with terms defined in the singular having comparable meanings when used in the plural), unless the context otherwise requires:

“Accreted Value” means, as of any date, with respect to each share of Series A Preferred Stock, the Stated Value Per Share, plus the amount of unpaid dividends that have accrued, compounded and been added thereto to such date pursuant to Section 3(a) hereof.

“Board of Directors” means the Board of Directors of the Corporation.

“Business Day” means any day except a Saturday, a Sunday, or other day on which commercial banks in the Commonwealth of Massachusetts are authorized or required by law or executive order to close.

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“Capital Stock” means, with respect to any Person, any and all shares, interests, participations, rights in, or other equivalents (however designated and whether voting or non-voting) of, such Person’s capital stock (including, without limitation, common stock and preferred stock) and any and all rights, warrants or options exchangeable for or convertible into such capital stock.

“Change of Control” means (i) any merger, consolidation or other business combination transaction (or series of related transactions) in which the shareholders owning a majority of the voting securities of the Corporation prior to such transaction do not own a majority of the voting securities of the surviving entity, (ii) any tender offer, exchange offer or other transaction whereby any person or “group” other than the holders of shares of Series A Preferred Stock obtains a majority of the outstanding shares of Common Stock, (iii) a sale of all or substantially all of the assets of the Corporation, (iv) any proxy contest in which a majority of the Board of Directors of the Corporation (or persons appointed by the Board of Directors) prior to such contest do not constitute a majority of the Corporation’s Board of Directors after such contest or (v) any other transaction described in any stockholder rights agreement or “poison pill,” if any, to which the Corporation is party, which may permit the holders of any rights or similar certificates to exercise the rights evidenced thereby.

“Closing Date” means the date of first issuance of a share of Series A Preferred Stock.

“Commission” means the United States Securities and Exchange Commission or any similar agency then having jurisdiction to enforce the Securities Act.

“Common Stock” shall mean the common stock, par value $0.01 per share, of the Corporation.

“Current Market Price” per share of Capital Stock of any Person means, as of the date of determination, (a) the average of the daily Market Price under clause (a), (b) or (c) of the definition thereof of such Capital Stock during the immediately preceding thirty (30) trading days ending on such date, and (b) if such Capital Stock is not then listed or admitted to trading on any national securities exchange, or quoted on the Nasdaq National Market or the Nasdaq SmallCap Market, or quoted in the over-the-counter market, then the Market Price under clause (d) of the definition thereof on such date.

“Indebtedness” means, as to any Person, (a) all obligations of such Person for borrowed money (including, without limitation, reimbursement and all other obligations with respect to surety bonds, letters of credit and bankers’ acceptances, whether or not matured), (b) all obligations of such Person to pay the deferred purchase price of property or services, except trade accounts payable and accrued commercial or trade liabilities arising in the ordinary course of business, (c) all interest rate and currency swaps, caps, collars and similar agreements or hedging devices under which payments are obligated to be made by such Person, whether periodically or upon the happening of a contingency, (d) all indebtedness created or arising under any conditional sale or other title retention agreement with respect to property acquired by such Person (even though

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the rights and remedies of the seller or lender under such agreement in the event of default are limited to repossession or sale of such property), (e) all obligations of such Person under any capital leases, (f) all indebtedness secured by any lien (other than liens in favor of lessors under leases other than leases included in clause (e)) on any property or asset owned or held by that Person regardless of whether the indebtedness secured thereby shall have been assumed by that Person or is non-recourse to the credit of that Person, and (g) any direct or indirect liability of such Person with respect to any indebtedness, lease, dividend, guaranty, letter of credit or other similar obligation of another Person.

“Liquidation” means the voluntary or involuntary liquidation under applicable bankruptcy or reorganization legislation, or the dissolution or winding up of the Corporation.

“Market Price” means, with respect to the Capital Stock of any Person, as of the date of determination, (a) the closing price of the Capital Stock on a national securities exchange or as quoted on the Nasdaq National Market or the Nasdaq SmallCap Market on such day, as reported by the Wall Street Journal; or (b) if the Capital Stock is quoted on the Nasdaq National Market or the Nasdaq SmallCap Market but no sale occurs on such day, the average of the closing bid and asked prices of the Capital Stock on the Nasdaq National Market or the Nasdaq SmallCap Market on such day, as reported by the Wall Street Journal; or (c) if the Capital Stock is not so listed or quoted, the average of the closing bid and asked prices of the Capital Stock in the U.S. over-the-counter market; or (d) if none of (a), (b) or (c) is applicable, a market price per share determined by the Board of Directors (acting in good faith pursuant to the exercise of its fiduciary duties).

“Per Share Price” initially shall be equal to the Stated Value Per Share (subject to adjustment pursuant to the provisions of Section 6 hereof).

“Person” means any individual, firm, corporation, partnership, trust, incorporated or unincorporated association, joint venture, joint stock company, limited liability company, governmental authority or other entity of any kind, and shall include any successor (by merger or otherwise) of such entity.

“Securities Act” means the Securities Act of 1933, as amended, and the rules and regulations of the Commission thereunder.

“Series A Preferred Stock” shall have the meaning ascribed to it in Section 1 hereof.

“Statement of Designations” means this Statement of Designations relating to the powers, designations, preferences and rights of the Series A Preferred Stock.

[Remainder of page intentionally left blank]

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IN WITNESS WHEREOF, the undersigned has executed this Statement of Designations as of September 12, 2003.

SONTRA MEDICAL CORPORATION
By:	/s/ Sean F. Moran
	Name: Sean F. Moran
	Title: Chief Financial Officer

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EX-5

EXHIBIT 5

BROWNE ROSEDALE & LANOUETTE LLP

31 St. James Avenue, Suite 830

Boston, Massachusetts 02116

            October 15, 2003

Sontra Medical Corporation

10 Forge Parkway

Franklin, Massachusetts 02038

Ladies and Gentlemen:

This opinion is furnished to you in connection with a Registration Statement on Form S-3 (the “Registration Statement”) filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), for the registration of an aggregate of 15,360,000 shares of Common Stock, $0.01 par value per share (the “Common Stock”), of Sontra Medical Corporation, a Minnesota corporation (the “Company”), consisting of (i) an aggregate of 7,560,000 shares of Common Stock issuable upon conversion of shares of the Company’s Series A Convertible Preferred Stock (the “Conversion Shares”), and (ii) an aggregate of 7,800,000 shares of Common Stock issuable upon the exercise of the Company’s Common Stock Purchase Warrants (the “Warrant Shares”), all of which Conversion Shares and Warrant Shares, if and when sold, will be sold by certain stockholders of the Company (the “Selling Stockholders”).

We have examined signed copies of the Registration Statement as filed with the Commission. We have also examined and relied upon minutes of meetings of the shareholders and the Board of Directors of the Company as provided to us by the Company, stock record books of the Company as provided to us by the Company, the Articles of Incorporation and By-Laws of the Company, each as restated and/or amended to date, the Statement of the Powers, Designations, Preferences and Rights of the Series A Convertible Preferred Stock of the Company (the “Certificate of Designations”), and such other documents as we have deemed necessary for purposes of rendering the opinions hereinafter set forth.

In our examination of the foregoing documents, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as copies, the authenticity of the originals of such latter documents and the legal competence of all signatories to such documents.

We assume that the appropriate action will be taken, prior to the offer and sale of the Conversion Shares or Warrant Shares, as the case may be, to register and qualify the Conversion Shares or Warrant Shares, as the case may be, for sale under all applicable state securities or “blue sky” laws.

We express no opinion herein as to the laws of any state or jurisdiction other than the state laws of the Commonwealth of Massachusetts, the Minnesota Business Corporation Act statute and the federal laws of the United States of America. To the extent that any other laws govern the matters as to which we are opining herein, we have assumed that such laws are identical to the state laws of the Commonwealth of Massachusetts, and we are expressing no opinion herein as to whether such assumption is reasonable or correct.

Based upon and subject to the foregoing, we are of the opinion that:

1. The Conversion Shares have been duly authorized, and when issued upon conversion of the shares of the Company’s Series A Convertible Preferred Stock in accordance with the terms of the Certificate of Designations, will be validly issued, fully paid and nonassessable; and

2. The Warrant Shares have been duly authorized, and when issued upon exercise of the Company’s Common Stock Purchase Warrants in accordance with the terms thereof, will be validly issued, fully paid and nonassessable.

It is understood that this opinion is to be used only in connection with the offer and sale of the Conversion Shares and the Warrant Shares while the Registration Statement is in effect and may not be used, quoted or relied upon for any other purpose nor may this opinion be furnished to, quoted to or relied upon by any other person or entity, for any purpose, without our prior written consent.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters. This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-B under the Securities Act and to the use of this Firm’s name therein and in the related Prospectus under the caption “Legal Matters.” In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

Very truly yours,

/s/ Browne Rosedale & Lanouette LLP

Browne Rosedale & Lanouette LLP

EX-23.2

EXHIBIT 23.2

INDEPENDENT AUDITOR’S CONSENT

We consent to the incorporation by reference in this Registration Statement of Sontra Medical Corporation on Form S-3 of our report, dated January 31, 2003, included in the Annual Report on Form 10-KSB of Sontra Medical Corporation for the year ended December 31, 2002. We also consent to the reference to our Firm under the caption “Experts” in the Prospectus, which is a part of this Registration Statement.

/s/ WOLF & COMPANY, P.C.

Wolf & Company, P.C.

Boston, Massachusetts

October 14, 2003

EX-99.4

EXHIBIT 99.4

THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED, SOLD, ASSIGNED, TRANSFERRED, PLEDGED, OR OTHERWISE DISPOSED OF UNLESS AND UNTIL SUCH SECURITIES ARE REGISTERED UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE ISSUER IS OBTAINED TO THE EFFECT THAT SUCH REGISTRATION IS NOT REQUIRED. THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUED UPON ITS EXERCISE ARE SUBJECT TO THE RESTRICTIONS ON TRANSFER SET FORTH IN SECTION 5 OF THIS WARRANT.

Warrant No.	Number of Shares:
	(subject to adjustment)
Date of Issuance:                     , 2003

SONTRA MEDICAL CORPORATION

Common Stock Purchase Warrant

Void after                             , 2008

Sontra Medical Corporation, a Minnesota corporation (the “Company”), for value received, hereby certifies that Dawson James Securities, a Division of Viewtrade Financial (including registered assigns, the “Registered Holder”), is entitled, subject to the terms set forth below, to purchase from the Company, at any time or from time to time on or after the date of issuance and on or before             , 2008 at not later than 5:00 p.m. (Boston, Massachusetts time) up to              shares of Common Stock, $.01 par value per share, of the Company (the “Common Stock”), at a purchase price of $1.20 per share. The shares purchasable upon exercise of this Warrant, and the purchase price per share, each as adjusted from time to time pursuant to the provisions of this Warrant, are hereinafter referred to as the “Warrant Shares” and the “Purchase Price,” respectively.

1. Registration Rights. The Warrant Shares possess registration rights on a pari passu basis to those registration rights granted by the Company to the Subscribers pursuant to the Subscription Agreements, dated as of September 12, 2003, by and between the Company and the Subscribers, as amended by the Series A Unit Supplemental Agreements dated as of September 12, 2003 (collectively, the “Subscription Agreements”).

2. Exercise.

(a) This Warrant may be exercised by the Registered Holder, in whole or in part, by surrendering this Warrant, with the purchase form appended hereto as Exhibit I duly

executed by such Registered Holder or by such Registered Holder’s duly authorized attorney, at the principal office of the Company, or at such other office or agency as the Company may designate, accompanied by payment in full, in lawful money of the United States, of the Purchase Price payable in respect of the number of Warrant Shares purchased upon such exercise.

(b) If on any date after the later of (i) the effectiveness of the Registration Statement (as defined in the Subscription Agreements), and (ii) the date on which Shareholder Approval (as defined in the Subscription Agreements) is obtained, the closing price of the Common Stock, as quoted on the Nasdaq National Market, the Nasdaq SmallCap Market or the principal exchange on which the Common Stock is listed, or if not so listed then in the over-the-counter market as published in The Wall Street Journal, for 20 consecutive trading days equals at least $4.00 (subject to adjustment in the event of any subdivision, combination or reclassification affecting the Common Stock), the Company shall have the right, at its option and upon 30 days written notice to the Registered Holder, to terminate this Warrant; provided that (i) the Registered Holder shall have the right to exercise this Warrant at any time prior to such termination pursuant to Section 2(a), and (ii) the Registration Statement shall be effective at all times during such 30-day notice period. Upon such termination, the Registered Holder shall have no further rights hereunder. The Registered Holder shall have the right to exercise the Warrant until the termination of the 30-day notice period, provided that such 30-day notice period terminates prior to                     , 2008.

(c) Each exercise of this Warrant shall be deemed to have been effected immediately prior to the close of business on the day on which this Warrant shall have been surrendered to the Company as provided in subsection 2(a) above. At such time, the person or persons in whose name or names any certificates for Warrant Shares shall be issuable upon such exercise as provided in subsection 2(d) below shall be deemed to have become the holder or holders of record of the Warrant Shares represented by such certificates.

(d) In the event of any exercise of the rights represented by this Warrant, certificates for the Shares so purchased shall be delivered to the Registered Holder within a reasonable time and, unless this Warrant has been fully exercised or has expired, a new Warrant representing the shares with respect to which this Warrant shall not have been exercised shall also be issued to the Holder within such reasonable time.

(e) For purposes of this Warrant, the per share fair market value of the Company’s Common Stock shall mean:

(i) If the Company’s Common Stock is publicly traded, the per share fair market value shall be the average of the closing prices of the Common Stock as quoted on the Nasdaq National Market, the Nasdaq SmallCap Market or the principal exchange on which the Common Stock is listed, or if not so listed then the fair market value shall be the average of the closing bid prices of the Common Stock in the over-the-counter market as published in The

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Wall Street Journal, in each case for the fifteen trading days ending five trading days prior to the date of determination of fair market value;

(ii) If the Company’s Common Stock is not so publicly traded, the per share fair market value shall be such fair market value as is determined in good faith by the Board of Directors of the Company after taking into consideration factors it deems appropriate, including, without limitation, recent sale and offer prices of the capital stock of the Company in private transactions negotiated at arm’s length.

(f) NOTWITHSTANDING ANY OTHER PROVISION OF THIS WARRANT, THIS WARRANT SHALL NOT BE EXERCISABLE UNLESS AND UNTIL SHAREHOLDER APPROVAL (AS DEFINED IN THE SUBSCRIPTION AGREEMENT) IS OBTAINED.

3. Adjustments.

(a) If outstanding shares of the Company’s Common Stock shall be subdivided into a greater number of shares or a dividend in Common Stock shall be paid in respect of Common Stock, the Purchase Price in effect immediately prior to such subdivision or at the record date of such dividend shall, simultaneously with the effectiveness of such subdivision or immediately after the record date of such dividend be proportionately reduced and the number of Warrant Shares issuable upon exercise of the Warrant immediately prior to such subdivision or the record date of such dividend shall, simultaneously with the effectiveness of such subdivision or immediately after the record date of such dividend, be proportionately increased. If outstanding shares of Common Stock shall be combined into a smaller number of shares, the Purchase Price in effect immediately prior to such combination shall, simultaneously with the effectiveness of such combination, be proportionately increased, and the number of Warrant Shares issuable upon exercise of this Warrant immediately prior to such combination shall, simultaneously with the effectiveness of such combination, be proportionately reduced.

(b) If there shall occur any capital reorganization or reclassification or change of securities of the class issuable upon exercise of this Warrant (other than a change in par value, or as a result of a subdivision or combination), or in case of any merger of the Company with or into another corporation (other than a merger with another corporation in which the Company is the surviving corporation), or in case of any sale of all or substantially all of the assets of the Company, the Company, or such successor or purchasing corporation, as the case may be, shall duly execute and deliver to the holder of this Warrant a new Warrant (in form and substance reasonably satisfactory to the holder of this Warrant), or the Company shall make appropriate provision without the issuance of a new Warrant, so that the holder of this Warrant shall have the right to receive, at a total purchase price not to exceed that payable upon the exercise of the unexercised portion of this Warrant, and in lieu of the shares of Common Stock theretofore issuable upon exercise of this Warrant, (i) the kind and amount of shares of stock, other securities, money and property receivable upon such reclassification, change, merger or sale by a

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holder of the number of shares of Common Stock then purchasable under this Warrant, or (ii) in the case of such a merger or sale in which the consideration paid consists all or in part of assets other than securities of the successor or purchasing corporation, at the option of the Registered Holder of this Warrant, the securities of the successor or purchasing corporation having a value at the time of the transaction equivalent to the fair market value per share of Common Stock at the time of the transaction, as determined pursuant to subsection 1(d) above. The provisions of this subsection 3(b) shall similarly apply to successive reclassifications, changes, mergers and transfers.

(c) In case the Company, at any time or from time to time prior to the exercise in full of this Warrant, shall take any action affecting its Common Stock similar to or having an effect similar to any of the actions described in this Paragraph 3 (but not including any action described in any such Paragraph) and the Board of Directors in good faith determines that it would be equitable in the circumstances to adjust the Purchase Price as a result of such action, then, and in each such case, the Purchase Price shall be adjusted in such manner and at such time as the Board of Directors in good faith determines would be equitable in the circumstances (such determination to be evidenced in a resolution, a certified copy of which shall be mailed to the holders of Warrants).

(d) When any adjustment is required to be made pursuant to this Section 3, the Company shall promptly mail to the Registered Holder a certificate setting forth the Purchase Price and the number of Warrant Shares issuable upon exercise of this Warrant after such adjustment and setting forth a brief statement of the facts requiring such adjustment. Such certificate shall also set forth the kind and amount of stock or other securities or property into which this Warrant shall be exercisable following such adjustment.

4. Fractional Shares. The Company shall not be required upon the exercise of this Warrant to issue any fractional shares, but shall make an adjustment therefor in cash on the basis of the fair market value per share of Common Stock, as determined pursuant to subsection 1(e) above.

5. Requirements for Transfer.

(a) This Warrant and the Warrant Shares shall not be sold or transferred unless either (i) they first shall have been registered under the Securities Act of 1933, as amended (the “Act”), or (ii) the Company first shall have been furnished with an opinion of legal counsel, reasonably satisfactory to the Company, to the effect that such sale or transfer is exempt from the registration requirements of the Act.

(b) Each certificate representing Warrant Shares shall bear a legend substantially in the following form:

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“The securities represented by this certificate have not been registered under the Securities Act of 1933, as amended, and may not be offered, sold or otherwise transferred, pledged or hypothecated unless and until such securities are registered under such Act or an opinion of counsel satisfactory to the Company is obtained to the effect that such registration is not required.”

The foregoing legend shall be removed from the certificates representing any Warrant Shares, at the request of the holder thereof, at such time as they become eligible for resale pursuant to Rule 144(k) under the Act.

6. Representations and Warranties of Registered Holder. The Registered Holder represents and warrants to the Company as follows:

(a) This Warrant and the Warrant Shares issuable upon exercise thereof are being acquired for the Registered Holder’s own account, not as nominee or agent, and not with a view to the resale or distribution of any part thereof in violation of the Act, and the Registered Holder has no present intention of selling, granting any participation in, or otherwise distributing the same in violation of the Act. The Registered Holder is not a registered broker dealer or an entity engaged in the business of being a broker dealer. The Registered Holder understands that this Warrant and the Warrant Shares issuable upon exercise thereof are characterized as “restricted securities” under the U.S. federal securities laws inasmuch as they are being acquired from the Company in a transaction not involving a public offering and that under such laws and applicable regulations such Warrant and the Warrant Shares issuable upon exercise thereof may be resold without registration under the Act only in certain limited circumstances.

(b) The Registered Holder has such knowledge and experience in financial and business matters that it is capable of evaluating the merits and risks of the purchase of this Warrant and the Warrant Shares purchasable pursuant to the terms of this Warrant and of protecting its interests in connection therewith.

(c) The Registered Holder is able to bear the economic risk of the purchase of the Warrant Shares pursuant to the terms of this Warrant.

7. Reservation of Stock. The Company will at all times reserve and keep available, solely for issuance and delivery upon the exercise of this Warrant, such number of Warrant Shares and other stock, securities and property, as from time to time shall be issuable upon the exercise of this Warrant; provided, however, that if at any time the Company shall not have sufficient shares so available, the Company shall promptly take corrective action to remedy such shortfall.

8. Exchange of Warrants. Upon the surrender by the Registered Holder of any Warrant or Warrants, properly endorsed, to the Company at the principal office of the Company,

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the Company will, subject to the provisions of Section 5 hereof, issue and deliver to or upon the order of such Registered Holder, at the Company’s expense, a new Warrant or Warrants of like tenor, in the name of such Registered Holder or as such Registered Holder (upon payment by such Registered Holder of any applicable transfer taxes) may direct, calling in the aggregate on the face or faces thereof for the number of shares of Common Stock called for on the face or faces of the Warrant or Warrants so surrendered.

9. Replacement of Warrants. Upon receipt of evidence reasonably satisfactory to the Company of the loss, theft, destruction or mutilation of this Warrant and (in the case of loss, theft or destruction) upon delivery of an indemnity agreement (with surety if reasonably required) in an amount reasonably satisfactory to the Company, or (in the case of mutilation) upon surrender and cancellation of this Warrant, the Company will issue, in lieu thereof, a new Warrant of like tenor.

10. Transfers, etc.

(a) The Company will maintain a register containing the names and addresses of the Registered Holders of this Warrant. Any Registered Holder may change its address as shown on the warrant register by written notice to the Company requesting such change.

(b) Subject to the provisions of Section 5 hereof, this Warrant and all rights hereunder are transferable, in whole or in part, upon surrender of this Warrant with a properly executed assignment (in the form of Exhibit II hereto) at the principal office of the Company.

(c) Until any transfer of this Warrant is made in the warrant register, the Company may treat the Registered Holder of this Warrant as the absolute owner hereof for all purposes; provided, however, that if and when this Warrant is properly assigned in blank, the Company may (but shall not be obligated to) treat the bearer hereof as the absolute owner hereof for all purposes, notwithstanding any notice to the contrary and with no liability whatsoever to the Registered Holder.

11. Mailing of Notices, etc. All notices and other communications from the Company to the Registered Holder of this Warrant shall be given by hand, by messenger, mailed by first-class certified, registered mail, postage prepaid, or by a nationally recognized overnight delivery company to the address furnished to the Company in writing by the last Registered Holder of this Warrant who shall have furnished an address to the Company in writing. All notices and other communications from the Registered Holder of this Warrant or in connection herewith to the Company shall be given by hand, by messenger, mailed by first-class certified or registered mail, postage prepaid, or by a nationally recognized overnight delivery company to the Company at its principal office set forth below. If the Company should at any time change the location of its principal office to a place other than as set forth in the preamble hereto, it shall give prompt written notice to the Registered Holder of this Warrant and thereafter all references in this Warrant to the location of its principal office at the particular time shall be as so specified in such notice.

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12. No Rights as Stockholder. Until the exercise of this Warrant, the Registered Holder of this Warrant shall not have or exercise any rights by virtue hereof as a stockholder of the Company.

13. Change or Waiver. Any term of this Warrant may be changed or waived only by an instrument in writing signed by the party against which enforcement of the change or waiver is sought.

14. Headings. The headings in this Warrant are for purposes of reference only and shall not limit or otherwise affect the meaning of any provision of this Warrant.

* * * * *

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15. Governing Law. This Warrant will be governed by and construed in accordance with the laws of the Commonwealth of Massachusetts.

SONTRA MEDICAL CORPORATION

By:

Name:

Title:

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EXHIBIT I

PURCHASE FORM

To: Sontra Medical Corporation 10 Forge Parkway Franklin, MA 02038 Attn: Chief Financial Officer Dated:                    

The undersigned, pursuant to the provisions set forth in the attached Warrant (No.         ), hereby irrevocably elects to purchase              shares of the Common Stock covered by such Warrant. The undersigned herewith makes payment of $                 in lawful money of the United States, representing the full purchase price for such shares at the price per share provided for in such Warrant.

Please issue a certificate or certificates representing said shares in the name of the undersigned or in such other name as is specified below:

(Name)

(Address)

The undersigned hereby represents and warrants that the aforesaid shares are being acquired for the account of the undersigned for investment and not with a view to, or for resale, in connection with the distribution thereof, and that the undersigned has no present intention of distributing or reselling such shares and all representations and warranties of the undersigned set forth in Section 6 of the attached Warrant are true and correct as of the date hereof.

Signature:

Address:

EXHIBIT II

ASSIGNMENT FORM

FOR VALUE RECEIVED,                                  hereby sells, assigns and transfers all of the rights of the undersigned under the attached Warrant (No.             ) with respect to the number of shares of Common Stock covered thereby set forth below, unto:

Name of Assignee	Address	Shares
Dated:	Signature:
Dated:	Witness: