Exhibit 5.1

May 9, 2007

Encysive Pharmaceuticals Inc.
4848 Loop Central Drive, Suite 700
Houston, Texas 77081

Re: Encysive Pharmaceuticals Inc. Registration Statement on Form S-8; 2007 Incentive Plan, as amended

Gentlemen:

     We have acted as counsel to Encysive Pharmaceuticals Inc., a Delaware corporation (the “Company”), in connection with the preparation for filing with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to the registration of 2,600,000 shares (the “Shares”) of the Company’s common stock, par value $.005 per share (the “Common Stock”), issuable pursuant to the Company’s 2007 Incentive Plan, as amended (the “Plan”).

     We have examined the Plan and such corporate records, documents, instruments and certificates of the Company, and have reviewed such questions of law as we have deemed necessary, relevant or appropriate to enable us to render the opinion expressed herein. In such examination, we have assumed without independent investigation the authenticity of all documents submitted to us as originals, the genuineness of all signatures, the legal capacity of all natural persons, and the conformity of any documents submitted to us as copies to their respective originals. As to certain questions of fact material to this opinion, we have relied without independent investigation upon statements or certificates of public officials and officers of the Company.

     Based upon such examination and review, we are of the opinion that the Shares have been duly and validly authorized and will, upon issuance and delivery as contemplated by the Plan, be validly issued, fully paid and nonassessable outstanding shares of Common Stock.

     This Firm consents to the filing of this opinion as an exhibit to the Registration Statement. In giving this consent, we do not admit that this Firm is in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Porter & Hedges, L.L.P.

PORTER & HEDGES, L.L.P.