EXHIBIT 32.1

                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 Quarterly Report on Form 10-Q of PAREXEL International
Corporation (the "Company") for the period ended December 31, 2005 as filed with
the Securities and Exchange Commission on the date hereof (the "Report"), the
undersigned, Josef H. von Rickenbach, Chief Executive Officer of the Company,
hereby certifies, pursuant to 18 U.S.C. Section 1350, that:

      (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 results of operations
            of the Company.

Date: February 9, 2006         /s/ Josef H. von Rickenbach
                               ---------------------------
                               Josef H. von Rickenbach
                               Chairman of the Board and Chief Executive Officer

A signed original of this written statement required by Section 906 has been
provided to PAREXEL International Corporation and will be retained by PAREXEL
International Corporation and furnished to the Securities and Exchange
Commission or its staff upon request.