SC 14D9/A

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14D-9

(Rule 14d-101)

Solicitation/Recommendation Statement Under Section 14(d)(4)

of the Securities Exchange Act of 1934

(Amendment No. 18)

Biosite Incorporated

(Name of Subject Company)

Biosite Incorporated

(Name of Person Filing Statement)

Common Stock, $0.01 par value per share

(Title of Class of Securities)

090945 10 6

(CUSIP Number of Class of Securities)

Kim D. Blickenstaff

Chairman and Chief Executive Officer

Biosite Incorporated

9975 Summers Ridge Road

San Diego, California 92121

(858) 805-2000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and

Communications on Behalf of Person Filing Statement)

With copies to:

David B. Berger, Esq.	Frederick T. Muto, Esq.
Vice President, Legal Affairs	Jason L. Kent, Esq.
Biosite Incorporated	Cooley Godward Kronish LLP
9975 Summers Ridge Road	4401 Eastgate Mall
San Diego, California 92121	San Diego, California 92121
(858) 805-2000	(858) 550-6000

¨ Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

This Amendment No. 18 to the Solicitation/Recommendation Statement on Schedule 14D-9 amends and supplements the Solicitation/Recommendation Statement on Schedule 14D-9 previously filed by Biosite Incorporated, a Delaware corporation (“Biosite”), with the Securities and Exchange Commission (the “SEC”) on April 2, 2007, as amended by Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4, Amendment No. 5, Amendment No. 6, Amendment No. 7, Amendment No. 8, Amendment No. 9, Amendment No. 10, Amendment No. 11, Amendment No. 12, Amendment No. 13, Amendment No. 14, Amendment No. 15, Amendment No. 16 and Amendment No. 17 to the Solicitation/Recommendation Statement on Schedule 14D-9 filed by Biosite with the SEC on April 5, 2007, April 10, 2007, April 10, 2007, April 16, 2007, April 17, 2007, April 18, 2007, April 20, 2007, April 24, 2007, April 25, 2007, April 26, 2007, April 26, 2007, April 30, 2007, May 2, 2007, May 8, 2007, May 10, 2007, May 11, 2007 and May 15, 2007 respectively (the Schedule 14D-9, as previously filed with the SEC and as the same has been or is amended or supplemented from time to time, the “Schedule 14D-9”). The Schedule 14D-9 relates to the tender offer made by Louisiana Acquisition Sub, Inc., a Delaware corporation and a wholly-owned subsidiary of Beckman Coulter, Inc. (“Beckman”), disclosed in a Tender Offer Statement on Schedule TO, dated April 2, 2007 (as the same has been or is amended or supplemented from time to time), to purchase all of the outstanding shares of common stock, $0.01 par value per share, of Biosite at a purchase price of $90.00 per share, net to the seller in cash, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated April 2, 2007 (as the same has been or is amended or supplemented from time to time), and in the related Letter of Transmittal. Any capitalized term used and not otherwise defined herein shall have the meaning ascribed to such terms in the Schedule 14D-9.

Item 8. Additional Information.

Item 8 of the Schedule 14D-9 is hereby further amended and supplemented by adding the following at the end of Item 8:

On May 14, 2007, Mr. Kim Blickenstaff, Biosite’s Chairman and Chief Executive Officer, sent an email to Biosite’s employees with respect to the May 14 Inverness Offer. A copy of the email is filed as Exhibit (a)(1)(MM) hereto and is incorporated herein by reference.

Also on May 14, 2007, Beckman issued a press release announcing that it would not be increasing the Offer Price. Mr. Blickenstaff and Dr. Kenneth Buechler, Biosite’s President and Chief Scientific Officer, subsequently sent an email to Biosite’s employees, a copy of which is filed as Exhibit (a)(1)(NN) hereto and is incorporated herein by reference.

Item 9.

Exhibit No.	Description
(a)(1)(MM)	Email to employees of Biosite Incorporated dated May 14, 2007.
(a)(1)(NN)	Email to employees of Biosite Incorporated dated May 14, 2007.

SIGNATURE

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BIOSITE INCORPORATED
By:	/s/ Christopher J. Twomey
Name:	Christopher J. Twomey
Title:	SVP, Finance, CFO and Secretary

Dated: May 15, 2007

EX-99.(A)(1)(MM)

Exhibit (a)(1)(MM)

From: Blickenstaff, Kim

Sent: Monday, May 14, 2007 6:45 PM

To: @Everyone

Subject: Biosite Determines that Revised Binding Offer from Inverness Constitutes a “Superior Proposal”

We announced this afternoon that our Board of Directors has determined that the revised binding offer it received from Inverness Medical Innovations, Inc. is a “Superior Proposal” as defined in the existing merger agreement between Beckman Coulter, Inc. and Biosite.

Beckman Coulter now has until 12:01 a.m., Pacific Daylight Time, on Friday, May 18, 2007 to make a binding offer. If Beckman Coulter does submit a binding offer, our Board of Directors will meet to determine if it is at least as favorable to our stockholders as the Superior Proposal made by Inverness. Further details can be found in the attached press release.

We recognize that you may have questions about this process and we will keep you informed of updates as they become available. Thank you for your continued commitment and understanding and for remaining focused through this process.

Additional Information and Where To Find It

Stockholders of Biosite are urged to read the relevant tender offer documents because they contain important information that stockholders should consider before making any decision regarding tendering their shares. Beckman Coulter and its acquisition subsidiary have filed tender offer materials with the SEC, and Biosite has filed a Solicitation/Recommendation Statement with respect to the tender offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other offer documents) and the Solicitation/Recommendation Statement contain important information, which should be read carefully before any decision is made with respect to the tender offer. The Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the solicitation/Recommendation Statement, are available to all stockholders of Biosite at no expense to them. The tender offer materials and the Solicitation/Recommendation Statement are available for free at the SEC’s website at http://www.sec.gov. In addition, stockholders are able to obtain a free copy of these documents from (i) Beckman Coulter by mailing requests for such materials to: Beckman Coulter, Inc., Office of Investor Relations (M/S A-37-C), 4300 N. Harbor Blvd., P. O. Box 3100, Fullerton, CA 92834 and (ii) Biosite by mailing requests for such materials to: Investor Relations, Biosite, 9975 Summers Ridge Road, San Diego, California 92121.

In addition to the tender offer materials described above, Biosite and Beckman Coulter file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information filed by Biosite or Beckman Coulter at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room. Biosite’s and Beckman Coulter’s filings with the SEC are also available to the public from commercial document-retrieval services and at the website maintained by the SEC at http://www.sec.gov.

FOR IMMEDIATE RELEASE

Contact:

Nadine Padilla

Vice President, Corporate & Investor Relations

(858) 805-2820

Joele Frank / Dan Katcher

Joele Frank, Wilkinson Brimmer Katcher

(212) 895-8627

BIOSITE DETERMINES THAT REVISED BINDING OFFER FROM

INVERNESS CONSTITUTES A “SUPERIOR PROPOSAL”

Beckman Coulter Has Right to Match Offer Under Merger Agreement

SAN DIEGO, May 14, 2007 – Biosite Incorporated (Nasdaq: BSTE) today announced that its Board of Directors has received a revised binding offer from Inverness Medical Innovations, Inc. (Amex: IMA) to acquire, by way of a cash tender offer, 100% of the outstanding shares of common stock of Biosite not already owned by Inverness. The price contemplated by the Inverness offer is $92.50 per share in cash, plus if the “Acceptance Time” of the Inverness tender offer (as defined in the proposed Inverness merger agreement) does not occur on or prior to the date that is 45 days from the date of the Inverness merger agreement (or the next succeeding business day) (the “Target Date”), an amount of cash equal to $0.015205 per day for each day during the period commencing on the day following the Target Date through the Acceptance Time of the Inverness tender offer.

The Inverness offer includes a merger agreement signed by Inverness, and was accompanied by copies of signed (and revised) commitment letters from Inverness’ proposed financing sources. Inverness’ offer states that the offer is irrevocable and will remain open until 5:00 p.m., Pacific Daylight Time, on Friday, May 18, 2007. Complete copies of the offer, the merger agreement signed by Inverness and the revised commitment letters are being filed with the SEC as exhibits to Amendment No. 17 to Biosite’s Schedule 14D-9 relating to Biosite’s existing merger agreement with Beckman Coulter, Inc. (NYSE: BEC).

Biosite also announced that its Board of Directors has determined that the binding offer from Inverness constitutes a “Superior Proposal” as defined in the existing merger agreement between Beckman Coulter and Biosite.

Pursuant to the terms of the existing merger agreement with Beckman Coulter, Biosite has transmitted to Beckman Coulter a written notice of Biosite’s current intention to terminate the Beckman Coulter merger agreement and accept the Inverness Superior Proposal after 12:01 a.m., Pacific Daylight Time, on Friday, May 18, 2007. While the

Biosite Board has not at this time effected a “Company Change in Recommendation” as defined in the merger agreement with Beckman Coulter, Biosite has transmitted to Beckman Coulter a written notice of the Biosite Board’s current intention to effect a Company Change in Recommendation in support of the Inverness Superior Proposal after 12:01 a.m., Pacific Daylight Time, on Friday, May 18, 2007. Beckman Coulter has until 12:01 a.m., Pacific Daylight Time, on Friday, May 18, 2007 to make a binding offer that the Biosite Board determines is at least as favorable to Biosite’s stockholders as the Superior Proposal made by Inverness.

Absent agreement on a revised transaction with Beckman Coulter, Biosite intends to terminate the Beckman Coulter merger agreement and enter into the proposed Inverness merger agreement. In the event Biosite so terminates the Beckman Coulter merger agreement, Beckman Coulter would be entitled to a $54 million termination fee from Biosite. The offer from Inverness provides that, immediately after the execution of the Inverness merger agreement by Biosite, Inverness will make a payment to Biosite in an amount equal to the termination fee paid by Biosite to Beckman Coulter.

As previously announced, a subsidiary of Beckman Coulter has commenced a cash tender offer pursuant to which such subsidiary is offering to acquire all of Biosite’s outstanding shares of common stock for $90.00 per share. Unless the tender offer is extended by Beckman Coulter, it and any withdrawal rights to which Biosite’s stockholders may be entitled will expire at 12:00 midnight, New York City time, on Tuesday, May 15, 2007 (the end of the day on Tuesday).

Goldman Sachs is acting as financial advisor to Biosite and Cooley Godward Kronish LLP and Potter Anderson & Corroon LLP are serving as legal advisors.

About Biosite

Biosite Incorporated is a leading bio-medical company commercializing proteomics discoveries for the advancement of medical diagnosis. The company’s products contribute to improvements in medical care by aiding physicians in the diagnosis of critical diseases and health conditions. The Biosite Triage^® rapid diagnostic tests are used in more than 70 percent of U.S. hospitals and in more than 60 international markets. Information on Biosite can be found at www.biosite.com.

Forward Looking Statements

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. These statements are based on current expectations, forecasts and assumptions. Actual results could differ materially from those anticipated by these forward-looking statements as a result of a number of factors, some of which may be beyond Biosite’s control. For a list and description of risks and uncertainties associated with Biosite’s businesses, see Biosite’s reports filed with the Securities and Exchange Commission (SEC), including the “Risk Factors” section in its most recent annual report on Form 10-K filed with the SEC. Biosite disclaims any

intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

Additional Information and Where To Find It

Stockholders of Biosite are urged to read the relevant tender offer documents because they contain important information that stockholders should consider before making any decision regarding tendering their shares. Beckman Coulter and its acquisition subsidiary have filed tender offer materials with the SEC, and Biosite has filed a Solicitation/Recommendation Statement with respect to the tender offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other offer documents) and the Solicitation/Recommendation Statement contain important information, which should be read carefully before any decision is made with respect to the tender offer. The Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the Solicitation/Recommendation Statement, are available to all stockholders of Biosite at no expense to them. The tender offer materials and the Solicitation/Recommendation Statement are available for free at the SEC’s website at http://www.sec.gov. In addition, stockholders are able to obtain a free copy of these documents from (i) Beckman Coulter by mailing requests for such materials to: Beckman Coulter, Inc., Office of Investor Relations (M/S A-37-C), 4300 N. Harbor Blvd., P. O. Box 3100, Fullerton, CA 92834 and (ii) Biosite by mailing requests for such materials to: Investor Relations, Biosite, 9975 Summers Ridge Road, San Diego, California 92121.

In addition to the tender offer materials described above, Biosite and Beckman Coulter file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information filed by Biosite or Beckman Coulter at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room. Biosite’s and Beckman Coulter’s filings with the SEC are also available to the public from commercial document-retrieval services and at the website maintained by the SEC at http://www.sec.gov.

EX-99.(A)(1)(NN)

Exhibit (a)(1)(NN)

From: Blickenstaff, Kim

Sent: Monday, May 14, 2007 9:59 PM

To: @Everyone

Subject: Merger Announcement

Following this evening’s announcement that Biosite has deemed Inverness’ offer a superior proposal, Beckman Coulter announced that they will not be increasing the price for their tender offer. Absent agreement on a revised transaction with Beckman Coulter, Biosite intends to terminate its existing agreement with Beckman Coulter and enter into the proposed Inverness merger agreement.

Tonight’s events have unfolded swiftly and as a result we do not yet have answers to the many questions you may have. Biosite’s management will be speaking with Inverness tomorrow and we are committed to providing you with more information by the end of the day on Wednesday, May 16, 2007.

We encourage you to please contact your director with questions or concerns and we look forward to providing you with an update as soon as we are able.

Sincerely,

Kim Blickenstaff

Chairman and Chief Executive Officer

Ken Buechler

President and Chief Scientific Officer

Additional Information and Where To Find It

Stockholders of Biosite are urged to read the relevant tender offer documents because they contain important information that stockholders should consider before making any decision regarding tendering their shares. Beckman Coulter and its acquisition subsidiary have filed tender offer materials with the SEC, and Biosite has filed a Solicitation/Recommendation Statement with respect to the tender offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other offer documents) and the Solicitation/Recommendation Statement contain important information, which should be read carefully before any decision is made with respect to the tender offer. The Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the solicitation/Recommendation Statement, are available to all stockholders of Biosite at no expense to them. The tender offer materials and the Solicitation/Recommendation Statement are available for free at the SEC’s website at http://www.sec.gov. In addition, stockholders are able to obtain a free copy of these documents from (i) Beckman Coulter by mailing requests for such materials to: Beckman Coulter, Inc., Office of Investor Relations (M/S A-37-C), 4300 N. Harbor Blvd., P. O. Box 3100, Fullerton, CA 92834 and (ii) Biosite by mailing requests

for such materials to: Investor Relations, Biosite, 9975 Summers Ridge Road, San Diego, California 92121.

In addition to the tender offer materials described above, Biosite and Beckman Coulter file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information filed by Biosite or Beckman Coulter at the SEC public reference room at 100 F Street, N.E., Washington, D.C.20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room. Biosite’s and Beckman Coulter’s filings with the SEC are also available to the public from commercial document-retrieval services and at the website maintained by the SEC at http://www.sec.gov.