EXHIBIT 99.1

Sontra Medical Corporation Reports First Quarter 2004 Financial Results

FRANKLIN, Mass., May 10 — Sontra Medical Corporation (Nasdaq SC: SONT) announced today financial results for the first quarter ended March 31, 2004. For the three months ended March 31, 2004, the net loss applicable to common stockholders was $1,403,000, or $.11 per share, as compared to $951,000, or $.10 per share, for the same period in 2003.

The Company’s cash balance increased from $4,869,000 at December 31, 2003 to $6,273,000 at March 31, 2004. On January 15, 2004, the Company received a $1.5 million payment from Bayer Health Care LLC’s Diagnostic Division pursuant to a license agreement executed in July 2003 for Sontra’s non-invasive glucose monitoring technology. Also during the first quarter, Sontra realized net proceeds of $1,036,000 from the exercise of warrants to purchase common stock issued in 2003.

First Quarter 2004 Highlights:

• In February, the FDA granted the Company the first 510(k) marketing clearance for SonoPrep(R) for use in electrophysiology applications.

• In early March, the Company submitted a 510(k) application for a second indication, seeking marketing clearance to use SonoPrep and its topical lidocaine procedure tray to achieve rapid skin anesthesia. This FDA submission was supported by data from three clinical studies involving approximately 500 patients that demonstrates that rapid skin anesthesia with 4% lidocaine was achieved within five minutes following a skin pretreatment with SonoPrep.

• During the quarter, the Company received approximately $2.54 million from a licensing payment and the exercise of warrants.

“We made solid progress during the first quarter in developing and expanding the value of our product pipeline,” stated Thomas W. Davison, PhD, Sontra’s President and Chief Executive Officer. “SonoPrep skin permeation technology clearly improves the clinical utility of topical lidocaine because existing products addressing this $100 million market require up to a 60- minute waiting period compared to five minutes following a skin pretreatment with SonoPrep before effective skin anesthesia is achieved. We expect to launch our product for this indication during the third quarter of 2004, assuming FDA 510(k) marketing clearance. Additionally, during 2004 we plan to conduct clinical studies demonstrating that SonoPrep enables transdermal delivery of vaccines and other pain drugs.”

About Sontra Medical Corporation

Sontra Medical Corporation is the pioneer of SonoPrep, a non-invasive ultrasound-mediated skin permeation technology that enables transdermal diagnosis and drug delivery. Sontra’s products under development include: a continuous non-invasive glucose monitor developed in collaboration with Bayer Diagnostics; a rapid onset (less than 5 minutes) topical anesthetic delivery system and the use of SonoPrep for the transdermal delivery of large molecule drugs and biopharmaceuticals. For additional information, please visit the Company’s website at www.sontra.com.

SonoPrep is a registered trademark of Sontra Medical Corporation. All other company, product or service names mentioned herein are the trademarks or registered trademarks of their respective owners.

This press release contains forward-looking statements, which address a variety of subjects including, for example, the expected future operating and financial results, including the sufficiency of cash balances to fund operations, the expected benefits, efficacy and market opportunity of the SonoPrep device and technology and related applications, and the expected timing of the commercial availability of the SonoPrep device and lidocaine procedure tray. Statements that are not historical facts, including statements about our beliefs and expectations, are forward-looking statements. Such statements are based on our current expectations and are subject to a number of factors and uncertainties, which could cause actual results to differ materially from those described in the forward-looking statements. The following important factors and uncertainties, among others, could cause actual results to differ materially from those described in these forward- looking statements: Sontra’s success depends on its ability to execute on its business strategy; Sontra may face difficulties or delays in obtaining regulatory approvals to market products resulting from development efforts; Sontra may experience adverse results in product development, clinical trials and commercialization efforts; Sontra may fail to obtain and maintain patent protection for discoveries; Sontra’s business strategy depends, in part, upon strategic partners to develop and commercialize products based on our work; and Sontra requires substantial funding to conduct research and development and to expand commercialization activities in accordance with its business plans. For detailed information about factors that could cause actual results to differ materially from those described in the forward-looking statements, please refer to Sontra’s filings with the Securities and Exchange Commission, including Sontra’s most recent Quarterly Report on Form 10-QSB. Forward- looking statements represent management’s current expectations and are inherently uncertain. We do not undertake any obligation to update forward-looking statements made by us.

SONTRA MEDICAL CORPORATION

Consolidated Statements of Loss

(Unaudited)

	For the Three Months Ended March 31,
	2004			2003
Revenues	$	—		$	—
Operating Expenses:
Research and development		675,907			541,352
General and administrative		527,494			418,433
Total operating expenses		1,203,401			959,785
Loss from operations		(1,203,401	)		(959,785	)
Interest income		14,229			9,106
Net loss		(1,189,172	)		(950,679	)
Accretion of dividend and beneficial conversion feature on Series A Convertible Preferred Stock		(213,434	)		—
Net loss applicable to common shareholders	$	(1,402,606	)	$	(950,679	)
Net loss per common share, basic and diluted	$	(0.11	)	$	(0.10	)
Basis and diluted weighted average common shares outstanding		12,711,051			9,360,938

SONTRA MEDICAL CORPORATION

Consolidated Balance Sheets

	As of
	March 31, 2004			December 31, 2003
	(Unaudited)
Assets:
Current Assets:
Cash and cash equivalents	$	6,272,650		$	4,868,933
Accounts receivable		—			1,500,000
Prepaid expenses and other current assets		114,728			66,075
Total current assets		6,387,378			6,435,008
Property and Equipment, at cost
Computer equipment		174,847			171,272
Office and laboratory equipment		407,735			405,285
Furniture and fixtures		14,288			14,288
Manufacturing equipment		180,608			144,695
Leasehold improvements		166,289			166,289
		943,767			901,829
Less-Accumulated depreciation and amortization		(534,835	)		(498,341	)
Net property and equipment		408,932			403,488
Other Assets:
Restricted cash		48,746			48,746
Other assets		2,000			2,000
Total other assets		50,746			50,746
Total assets	$	6,847,056		$	6,889,242
Liabilities and Stockholders’ Equity
Current Liabilities:
Accounts payable	$	126,001		$	136,810
Accrued expenses		283,600			465,092
Total current liabilities		409,601			601,902
Commitments
Stockholders’ Equity:
Series A Convertible Preferred Stock, $0.01 par value, authorized 7,000,000 shares, issued and outstanding 2,987,500 shares at March 31, 2004 and 6,495,000 shares at December 31, 2003 (preference in liquidation of $3,105,148)		3,105,148			6,628,842
Common stock, $0.01 par value, authorized 40,000,000 shares, issued and outstanding 14,521,635 shares at March 31, 2004 and 10,102,992 shares at December 31, 2003		145,216			101,030
Additional paid-in capital		22,802,718			17,952,721
Deferred stock-based compensation		(404,076	)		(372,874	)
Accumulated deficit		(19,211,551	)		(18,022,379	)
Total stockholders’ equity		6,437,455			6,287,340
Total liabilities and stockholders’ equity	$	6,847,056		$	6,889,242