Exhibit 5.1

October 12, 2004

Lightbridge, Inc.
30 Corporate Drive
Burlington, MA 01803

      RE:   S-8 REGISTRATION STATEMENT

Ladies and Gentlemen:

      We have acted as counsel for Lightbridge, Inc., a Delaware corporation
(the "Company"), in connection with the preparation and filing with the
Securities and Exchange Commission under the Securities Act of 1933, as amended
(the "Act"), of a Registration Statement on Form S-8 (the "Registration
Statement") relating to the offering by the Company of 2,500,000 shares (the
"Shares") of its common stock, $.01 par value ("Common Stock"), issuable
pursuant to the Lightbridge, Inc. 2004 Stock Incentive Plan (the "Plan"). The
Shares are in addition to an aggregate of 5,350,000 shares of Common Stock
originally issuable pursuant to prior stock option plans of the Company, which
shares were previously registered under the Act and are now issuable under the
Plan.

      In arriving at the opinions expressed below, we have examined and relied
on the following documents:

      (i)   the Registration Statement;

      (ii)  the Plan;

      (iii) the Certificate of Incorporation and By-Laws of the Company; and

      (iv)  the records of meetings and consents of the Board of Directors and
            stockholders of the Company provided to us by the Company.

      In addition, we have examined and relied on the originals or copies
certified or otherwise identified to our satisfaction of all such records,
documents and instruments of the Company and such other persons, and we have
made such investigations of law, as we have deemed appropriate as a basis for
the opinions expressed below.



Lightbridge, Inc.
October 12, 2004

      We express no opinion other than as to the General Corporation Law of the
State of Delaware.

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

      1.    The Company has the corporate power necessary for the issuance of
            the Shares under the Plan, as contemplated by the Registration
            Statement.

      2.    The Shares have been duly authorized by all necessary corporate
            action and, when issued against payment of the agreed consideration
            therefor in accordance with the Plan, will be validly issued, fully
            paid and non-assessable.

      We consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement. 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 of 1933 or the rules and regulations of the Securities and
Exchange Commission.

                                                Very truly yours,

                                                FOLEY HOAG LLP

                                                By:  /s/ Alexander H. Pyle
                                                     --------------------------
                                                     a Partner