UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                -----------------

                                    FORM 8-K


                                 CURRENT REPORT
                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

        Date of Report (Date of earliest event reported): April 20, 2006


                                ICOS CORPORATION
             (Exact name of registrant as specified in its charter)

         Washington                   0-19171                   91-1463450
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(State or other jurisdiction of     (Commission              (I.R.S. Employer
incorporation or organization)      File Number)             Identification No.)


                 22021 - 20th Avenue S.E., Bothell, WA    98021
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             (Address of principal executive offices)   (Zip code)


                                 (425) 485-1900
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              (Registrant's telephone number, including area code)


                                 Not Applicable
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              (Former name, former address and former fiscal year,
                         if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions:

[ ]  Written communications pursuant to Rule 425 under the Securities Act
    (17 CFR 230.425)

[ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act
    (17 CFR 240.14a-12)

[ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the
    Exchange Act (17 CFR 240.14d-2(b))

[ ] Pre-commencement communications pursuant to Rule 13e4(c) under the
    Exchange Act (17 CFR 240.13e-4(c))








ITEM 2.02.    Results of Operations and Financial Condition

              On April 20, 2006, Lilly ICOS LLC, our 50/50 joint venture with
Eli Lilly and Company, which is marketing Cialis(R) (tadalafil) for the
treatment of erectile dysfunction, issued a press release announcing its
financial results for the quarter ended March 31, 2006. A copy of the press
release is furnished as Exhibit 99 to this report and is incorporated herein by
reference.


                                    SIGNATURE


              Pursuant to the requirements of the Securities Exchange Act of
1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned thereunto duly authorized.

                                              ICOS CORPORATION


Date:    April 20, 2006                        By:   /S/ MICHAEL A. STEIN
         --------------                              --------------------
                                                     Michael A. Stein
                                                     Senior Vice President and
                                                     Chief Financial Officer




                                  EXHIBIT INDEX

Exhibit No.          Description

99                   Press Release of Lilly ICOS LLC dated April 20, 2006,
                     reporting Lilly ICOS' financial results for the quarter
                     ended March 31, 2006.