HALE AND DORR
                                60 State Street
                                Boston, MA 02109

                                                              September 30, 1996



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-1, together with Amendment No. 1 thereto (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 2,666,667 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. 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."


September 30, 1996
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


                                                            HALE AND DORR