HALE AND DORR LLP
                                60 State Street
                                Boston, MA 02109

                                                            February 28, 1997



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

Ladies and Gentlemen:

This opinion is furnished to you in connection with a Registration Statement on
Form S-1 (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 2,100,000 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., Alex. Brown & Sons Incorporated and Cowen & Company,
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."


February 28, 1997
Page 2


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