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                                                                     EXHIBIT 5.1


                     OPINION OF FULBRIGHT & JAWORSKI L.L.P.

                   [Letterhead of Fulbright & Jaworski L.L.P.]

November 8, 1999

Cambio Inc.
6006 North Mesa Street
El Paso, Texas 79912

Dear Sir or Madam:

         We refer to the Registration Statement on Form S-3 (the "Registration
Statement"), filed by Cambio Inc. (the "Company") on behalf of certain selling
stockholders with the Securities and Exchange Commission under the Securities
Act of 1933, as amended (the "Act"), relating to 31,082,562 shares of the
Company's Common Stock, $.01 par value (the "Shares"), of which 25,536,500
shares are issuable upon conversion of the Company's Series B Convertible
Preferred Stock, $.01 par value (the "Series B Preferred"), 1,256,495 shares are
issuable upon the exercise of warrants (the "Warrants") and 2,747,747 shares are
issuable upon the exercise of employee options (the "Employee Options.")

         As counsel for the Company, we have examined such corporate records,
documents and such questions of law as we have considered necessary or
appropriate for the purposes of this opinion and, upon the basis of such
examination, advise you that in our opinion the Shares issuable upon the
conversion of the Series B Preferred and the exercise of the Warrants and the
Employee Options have been duly and validly authorized and, subsequent to the
conversion of the Series B Preferred, and in the case of the Warrants and the
Employee Options, payment of the exercise price therefor, will be legally
issued, fully paid and nonassessable.

         We consent to the filing of this opinion as an exhibit to the
Registration Statement and the reference to this firm under the caption "Legal
Matters" in the prospectus contained therein and elsewhere in the Registration
Statement and prospectus. This consent is not to be construed as an admission
that we are a party whose consent is required to be filed with the Registration
Statement under the provisions of the Act.

                                                          Very truly yours,