Exhibit 5

August 14, 2007

Isolagen, Inc.

405 Eagleview Blvd.

Exton, PA 19341

Gentlemen:

You have requested our opinion with respect to certain matters in connection with the offering by Isolagen, Inc., a Delaware corporation (the “Company”), of an aggregate of 6,767,647 shares of the Company’s common stock, par value $0.001 (the “Shares”), pursuant to a Registration Statement on Form S-3 (Registration Statement No. 333-142959) (the “Registration Statement”), filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act” ), the prospectus included within the Registration Statement (the “Base Prospectus”), and the supplemented form of prospectus relating to the Shares dated August 14, 2007 and filed with the Commission pursuant to Rule 424(b) of the Rules and Regulations of the Act (the “Prospectus Supplement “). (The Base Prospectus and Prospectus Supplement are collectively referred to as the “Prospectus.”) All of the Shares are to be sold by the Company as described in the Registration Statement and Prospectus.

In connection with this opinion letter, we have examined the Registration Statement, the Prospectus, originals, or copies certified or otherwise identified to our satisfaction, of the Company’s certificate of incorporation and bylaws, and any amendments thereto, and such other documents, records and other instruments as we have deemed appropriate for purposes of the opinion set forth herein.

In our examination, we have assumed (a) the authenticity of original documents and the genuineness of all signatures, (b) the conformity to the originals of all documents submitted to us as copies or telecopies, and (c) the truth, accuracy and completeness of the information, representations and warranties contained in the records, documents, instruments and certificates we have reviewed.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold in accordance with the Registration Statement and Prospectus, will be validly issued, fully paid and nonassessable.

This opinion is limited to the Federal law of the United States, and the applicable statutory provisions of General Corporation Law of the State of Delaware, including all applicable provisions of the Delaware Constitution.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the reference made to this firm in the Registration Statement under the heading “Legal Matters.”

In giving such consent, we do not believe that we are “experts” within the meaning of such term used in the Securities Act or the rules and regulations of the Securities and Exchange Commission issued thereunder with respect to any part of the Registration Statement, including this opinion as an exhibit or otherwise.

Very truly yours,

Cozen O’Connor