EXHIBIT 5.1

                                   May 2, 2003

PAREXEL International Corporation
195 West Street
Waltham, MA 02451-1163

   Re:      Registration Statement on Form S-8

Ladies and Gentlemen:

            This opinion is furnished to you in connection with a Registration
Statement on Form S-8 (the "Registration Statement") filed with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended (the "Securities Act"), for the registration of 1,000,000 shares of
Common Stock, $.01 par value per share (the "Shares"), of PAREXEL International
Corporation, a Massachusetts corporation (the "Company"), issuable under the
Company's 2000 Employee Stock Purchase Plan (the "Plan").

            We have examined the Articles of Organization and By-Laws of the
Company, each as amended and restated to date, and originals, or copies
certified to our satisfaction, of all pertinent records of the meetings of the
directors and stockholders of the Company, the Registration Statement and such
other documents relating to the Company as we have deemed material for the
purposes of this opinion.

            In examination of the foregoing documents, we have assumed the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as copies, the authenticity of the originals of such latter documents and the
legal competence of all signatories to such documents.

            We express no opinion herein as to the laws of any state or
jurisdiction other than the state laws of the Commonwealth of Massachusetts and
the federal laws of the United States of America.

            Based upon and subject to the foregoing, we are of the opinion that
the Shares have been duly authorized for issuance and the Shares, when issued
and paid for in accordance with the terms of the Plan, will be validly issued,
fully paid and nonassessable.

            It is understood that this opinion is to be used only in connection
with the offer and sale of the Shares while the Registration Statement is in
effect.

            Please note that we are opining only as to the matters expressly set
forth herein, and no opinion should be inferred as to any other matters.

            We hereby consent to the filing of this opinion with the Commission
as an exhibit to the Registration Statement in accordance with the requirements
of Item 601(b)(5) of Regulation S-K under the Securities Act. In giving such
consent, we do not hereby admit that we are in the category of persons whose
consent is required under Section 7 of the Securities Act or the rules and
regulations of the Commission.

                                Very truly yours,

                                /s/ Hale and Dorr LLP

                                Hale and Dorr LLP