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                                  United States
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  FORM 20-F/A1

(Mark One)

 / /       REGISTRATION STATEMENT PURSUANT TO SECTION 12(b) OR (g) OF
                       THE SECURITIES EXCHANGE ACT OF 1934
                                       OR
 /X/             ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934
                     For the fiscal year ended: May 31, 2005
                                       OR
 / /          TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

               For the transition period from _______ to _______.

                         Commission file number: 1-13896

                           ICON public limited company
             (Exact name of Registrant as specified in its charter)

                                     Ireland
                 (Jurisdiction of incorporation or organization)

          South County Business Park, Leopardstown, Dublin 18, Ireland
                    (Address of principal executive offices)
                          _____________________________

              Securities registered or to be registered pursuant to
                            Section 12(b) of the Act:

                                      None

 Securities registered or to be registered pursuant to Section 12(g) of the Act:

American Depositary Shares, representing Ordinary Shares, par value euro 0.06
each ordinary Share, par value euro 0.06 each

Securities for which there is a reporting obligation pursuant to Section 15(d)
of the Act:

                                      None
                                    --------
                                (Title of Class)

Indicate the number of outstanding shares of each of the issuer's classes of
capital or common stock as of the close of the period covered by the annual
report: 13,899,096 Ordinary Shares

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days:

                  Yes:  /X/                      No: / /

Indicate by check mark which financial statement item the registrant has elected
to follow:

                  Item 17:                       Item 18: /X/

<PAGE>

                                EXPLANATORY NOTE

     This Amendment on Form 20-F/A1 (this "Amendment") to the Annual Report on
Form 20-F of ICON public limited company ("ICON") for the fiscal year ended May
31, 2005 (the "Form 20-F") is being filed by ICON solely for the purpose of
correcting the exhibits containing the certifications of the principal financial
officer of ICON and the date of the consent of the independent registered public
accounting firm. No other information in the Form 20-F has been changed from the
previous filing.

Part III

Item 19 EXHIBITS


The following exhibits are being filed as part of this Amendment:

Certifications of the Principal Financial Officer required by Rule 13a-14(a) of
the Securities Exchange Act of 1934, as amended

Consent of Independent Registered Public Accounting Firm

<PAGE>


SIGNATURES

     Pursuant to the requirements of Section 12 of the Securities Exchange Act
of 1934, the Registrant certifies that it meets all of the requirements for
filing on Form 20-F and has duly caused this annual report to be signed on its
behalf by the undersigned thereunto duly authorized.

                                ICON public limited company

                                /s/ Sean Leech
                                ------------------------------------------------
                                Sean Leech
                                Executive Vice President --
                                Commercial and Organizational Development
                                (Principal Financial Officer)*

Date: October 13, 2005



* Sean Leech, Executive Vice President -- Commercial and Organizational
Development, was replaced by Ciaran Murray as the chief financial officer of the
Registrant on October 3, 2005. Sean Leech is the person performing the functions
of the principal financial officer of the Registrant on an interim basis as of
the date hereof.


                                       3

<PAGE>



                  Certification of Principal Financial Officer
                           Pursuant to Section 302 of
                         the Sarbanes-Oxley Act of 2002


I, Sean Leech, Executive Vice President -- Commercial and Organizational
Development and the person performing the functions of the principal financial
officer of ICON plc (the "registrant") on an interim basis as of the date
hereof, certify that:

1. I have reviewed this annual report on Form 20-F of the registrant.

2. Based on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact necessary to make the statements
made, in light of the circumstances under which such statements were made, not
misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material respects the
financial condition, results of operations and cash flows of the registrant as
of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) and have:

          a) Designed such disclosure controls and procedures, or caused such
     disclosure controls and procedures to be designed under our supervision, to
     ensure that material information relating to the registrant, including its
     consolidated subsidiaries, is made known to us by others within those
     entities, particularly during the period in which this report is being
     prepared;


          b) Evaluated the effectiveness of the registrant's disclosure controls
     and procedures and presented in this report our conclusions about the
     effectiveness of the disclosure controls and procedures, as of the end of
     the period covered by this report based on such evaluation; and

          c) Disclosed in this report any change in the registrant's internal
     control over financial reporting that occurred during the period covered by
     the annual report that has materially affected, or is reasonably likely to
     materially affect, the company's internal control over financial reporting.

5. The registrant's other certifying officer and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
registrant's auditors and the audit committee of registrant's board of directors
(or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or
operation of internal control over financial reporting which are reasonably
likely to adversely affect the registrant's ability to record, process,
summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other
employees who have a significant role in the registrant's internal control over
financial reporting.

Dated: October 13, 2005


/s/ Sean Leech
_________________
Sean Leech
Executive Vice President --
Commercial and Organizational Development
(Principal Financial Officer)

                                       4

<PAGE>


                Certification Pursuant to 18 U.S.C. Section 1350,
      As Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002



In connection with the Annual Report of ICON plc (the "Company") on Form 20-F
for the period ending May 31, 2005, as filed with the Securities and Exchange
Commission on the date hereof (the "Report"), I, Sean Leech, Executive Vice
President -- Commercial and Organizational Development and the person performing
the functions of the principal financial officer of the Company on an interim
basis as of the date hereof, certify, pursuant to 18 U.S.C. ss. 1350, as adopted
pursuant to ss. 906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:
(1) the Report fully complies with the requirements of section 13(a) or 15(d) of
the Securities Exchange Act of 1934; and (2) The information contained in the
Report fairly presents, in all material respects, the financial condition and
result of operations of the Company.

Date:     October 13, 2005

/s/ Sean Leech
------------------
Sean Leech
Executive Vice President --
Commercial and Organizational Development
(Principal Financial Officer)

The foregoing certification is being furnished solely pursuant to section 906 of
the Sarbanes-Oxley Act of 2002 (subsections (a) and (b) of section 1350, chapter
63 of title 18, United States Code) and is not being filed as part of the report
or as a separate disclosure document. A signed original of this written
statement required by section 906 has been provided to ICON plc and will be
retained by ICON plc and furnished to the Securities and Exchange Commission or
its staff upon request.



                                       5

<PAGE>

            Consent of Independent Registered Public Accounting Firm



ICON plc
South County Business Park
Leopardstown
Dublin 18


We consent to the incorporation by reference in the registration statement on
Form S8 of ICON plc of our report dated July 27, 2005 with respect to the
consolidated balance sheets of ICON plc as of May 31, 2004 and 2005, and the
related consolidated statements of operations, shareholders' equity and
comprehensive income and cash flows, for each of the years in the three-year
period ended May 31, 2005, which report appears in the May 31, 2005, annual
report on Form 20-F of ICON plc.



KPMG
Public Accounting Firm

Dublin, Ireland
October 13, 2005