EXHIBIT 5.1 [LETTERHEAD] 404/572-4676 404/572-5147 April 16, 1998 Magellan Health Services, Inc. 3414 Peachtree Road, N.E. Suite 1400 Atlanta, Georgia 30326 Re: 2,566,622 Shares of Common Stock, $.25 par value per share, of Magellan Health Services, Inc. --------------------------------------------------------------- Gentlemen: We have acted as counsel to Magellan Health Services, Inc. (the "Company"), in connection with the preparation and filing of a Registration Statement on Form S-3 (the "Registration Statement"), for registration under the Securities Act of 1933, as amended, of 2,566,622 shares of Common Stock, $.25 par value per share, of the Company (the "Common Stock"). The shares of Common Stock are issuable upon the exercise of the Stock Purchase Warrants (collectively, the "Stock Purchase Warrants") issued by the Company to each of Crescent Operating, Inc. and Crescent Real Estate Equities Limited Partnership. In rendering the opinions expressed below we have examined the Registration Statement, the Stock Purchase Warrants, and such other documents as we have deemed necessary to enable us to express the opinions hereinafter set forth. In addition, we have examined and relied, to the extent we deemed proper, on certificates of officers of the Company as to factual matters, on the originals or copies certified or otherwise identified to our satisfaction of all such corporate records of the Company and such other instruments and certificates of public officials and other persons as we have deemed appropriate. In our examination, we have assumed the authenticity of all documents submitted to us as originals, the conformity to the original documents of all documents submitted to us as copies, and the genuineness of all signatures on documents reviewed by us and the legal capacity of natural persons. Based upon and subject to the foregoing, we are of the opinion that all legal and corporate proceedings necessary for the authorization and issuance of the shares of Common Stock to be issued by the Company pursuant to the Stock Purchase Warrants have been duly taken and the shares of Common Stock, upon issuance pursuant to the terms of the Stock Purchase Warrants, will be duly authorized, validly issued, fully paid and nonassessable. We hereby consent to (a) the filing of the foregoing legal opinion as an exhibit to the Registration Statement and all amendments thereto and (b) all references to our firm in the Registration Statement. Very truly yours /s/ KING & SPALDING --------------------------------------- King & Spalding