EXHIBIT 5

                               HALE AND DORR LLP
                                60 State Street
                               Boston, MA 02109


                                  May 1, 1998


International Telecommunication Data Systems, Inc.
969 High Ridge Road
Stamford, CT 06905

Ladies and Gentlemen:

     This opinion is furnished to you in connection with a Registration
Statement on Form S-3 (the "Registration Statement"), filed with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended, relating to the public offering of an aggregate of 4,945,000 shares of
Common Stock, $.01 par value per share (the "Shares"), of International
Telecommunication Data Systems, Inc., a Delaware corporation (the "Company").

     The Shares are to be sold by the Company and the selling stockholders
pursuant to an underwriting agreement (the "Underwriting Agreement") among the
Company and Lehman Brothers Inc., BT Alex. Brown Incorporated, Cowen & Company
and Jefferies & Company, Inc., as representatives of the several underwriters
named in the Underwriting Agreement (the "Underwriters").

     We have examined signed copies of the Registration Statement and all
exhibits thereto, all as filed with the Commission. We have also examined and
relied upon the original or copies of minutes of meetings of the stockholders
and Board of Directors of the Company, stock record books of the Company, a
copy of the By-Laws of the Company, as amended, and a copy of the Certificate
of Incorporation of the Company, as amended.

     Based upon the foregoing, we are of the opinion that the Shares have been
duly authorized for issuance and, after payment therefor and the issuance of
the certificates therefor by the Company in accordance with the terms of the
Underwriting Agreement, will be validly issued, fully paid and nonassessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name therein and in the related
Prospectus under the caption "Legal Matters."

     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.
 




                                                  Very truly yours,


                                                  /s/ HALE AND DORR LLP


                                                  HALE AND DORR LLP