Exhibit 5

                        [Dewey Ballantine LLP Letterhead]

June 26, 1998

Omnicare, Inc.
50 East RiverCenter Blvd. -- Suite 1530
Covington, Kentucky 41011

Ladies and Gentlemen:

      We have acted as special counsel to Omnicare, Inc., a Delaware corporation
("Omnicare"), in connection with the filing by Omnicare of a Registration
Statement on Form S-8 (the "Registration Statement") under the Securities Act of
1933 for the registration of up to 213,401 shares of common stock, $1.00 par
value per share (the "Shares"), of Omnicare which may be issued under the 1996
Stock Option Plan of CompScript, Inc., as amended, referred to therein (the
"Plan").

      For the purpose of rendering the opinion set forth herein, we have been
furnished with and examined such certificates and other documents as we have
deemed necessary or advisable for the purpose of expressing the opinion
contained herein.

      With respect to all of the documents reviewed, we have assumed, without
investigation, the genuineness of all signatures, the authenticity of all
documents submitted to us as originals and the conformity to originals of all
documents submitted to us as certified or reproduced copies.

      We are admitted to the Bar of the State of New York and express no opinion
as to the laws of any other jurisdiction other than the General Corporation Law
of the State of Delaware.

      Based on and subject to the foregoing, we are of the opinion that the
issuance of the Shares upon exercise of the options contemplated by the Plan
(the "Options"), has been duly authorized by Omnicare and when the Shares have
been issued as authorized in accordance with the terms of the Options, the
Shares will be validly issued, fully paid and nonassessable.

      We hereby consent to the filing of this opinion as Exhibit 5 to the
Registration Statement. In giving such consent, we do not thereby admit that we
come within 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 thereunder.

                                                     Very truly yours,


                                                     /s/ Dewey Ballantine LLP

                                                     DEWEY BALLANTINE LLP