1 [LETTERHEAD OF KEATING, MUETHING & KLEKAMP] FACSIMILE (513) 579-6956 May 14, 1996 Direct Dial: (513) 579-6468 EXHIBIT 5 Meridian Diagnostics, Inc. 3471 River Hills Drive Cincinnati, Ohio 45246 Gentlemen: We have examined the corporate records and proceedings of Meridian Diagnostics, Inc. (the "Corporation") with respect to: 1. The organization of the Corporation; and 2. The legal sufficiency of all corporate proceedings of the Corporation in connection with the creation and issuance of all of the present outstanding and issued shares of Common Stock, no par value, of the Corporation (the "Common Stock"). Based upon such examination, we are of the opinion: 1. That the Corporation is a duly organized and validly existing corporation in good standing under the laws of the State of Ohio; and 2. That the 100,000 shares of Common Stock, plus up to 15,000 which may be sold pursuant to an over-allotment option, all of which are being sold by the selling shareholder are duly authorized, legally issued, fully paid and non-assessable shares of Common Stock free of any claim of pre-emptive rights. 5 2 We hereby consent to be named in the Registration Statement and the Prospectus part thereof as the attorneys who will pass upon legal matters in connection with the aforesaid shares of Common Stock and to the filing of this opinion as an exhibit to the Registration Statement, and furthermore consent to all references made to this firm in the Registration Statement. Yours truly, KEATING, MUETHING & KLEKAMP BY: /s/ Edward E. Steiner -------------------------- Edward E. Steiner 6