August 27, 1996


Lightbridge, Inc.
281 Winter Street
Waltham, Massachusetts 02154

Ladies and Gentlemen:

   This opinion is furnished to you in connection with Amendment No. 2 to
Registration Statement on Form S-1 (Registration No. 333-6589) (the
"Registration Statement") being filed on the date hereof by Lightbridge, Inc., a
Delaware corporation (the "Company"), with the Securities and Exchange
Commission under the Securities Act of 1933, as amended.  The Registration
Statement relates to the proposed public offering by the Company of 3,021,868
shares (the "Company Shares") of its Common Stock, $.01 par value per share, to
be issued by the Company, and the proposed public offering by certain
securityholders of the Company of 1,348,132 shares of such Common Stock,
consisting of certain shares (the "Outstanding Shares") that are currently
issued and outstanding and certain shares (the "Warrant Shares") that are to be
issued upon the exercise of a warrant (the "Warrant"). The foregoing assumes
exercise in full of the over-allotment option described in the Registration
Statement. The Company Shares, the Outstanding Shares and the Warrant Shares are
to be sold pursuant to an underwriting agreement (the "Underwriting Agreement")
to be entered into among the Company, the holders of the Outstanding Shares and
the Warrant, and Cowen & Company, Montgomery Securities and Prudential
Securities Incorporated, as representatives of the several underwriters.

   We are familiar with the Company's Certificate of Incorporation and all
amendments thereto, its By-Laws and all amendments thereto, records of meetings
and consents of its Board of Directors and stockholders, and its stock records.
We have examined such other records and documents as we deemed necessary or
appropriate for purposes of rendering this opinion.

   Based upon the foregoing, we are of the opinion that:

   1. The Company Shares have been duly authorized and, when certificates for
the Company Shares have been duly executed and countersigned and delivered in
accordance with the Underwriting Agreement, the Company Shares will be validly
issued, fully paid and non-assessable.

   2. The Outstanding Shares have been duly authorized and are validly issued,
fully paid and non-assessable.

   3. The Warrant Shares have been duly authorized and, when the Warrant has
been exercised in accordance with its terms and a certificate for the Warrant
Shares has been duly executed, countersigned and delivered, the Warrant Shares
will be validly issued, fully paid and non-assessable.

 
   We consent to the filing of this opinion as an exhibit to the Registration
Statement and to the reference to us under the heading "Legal Matters" in the
prospectus forming part of the Registration Statement.

                                  Very truly yours,

                                  FOLEY, HOAG & ELIOT LLP



                                  By  /s/ Mark L. Johnson
                                    ----------------------------------
                                     A Partner