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                                                                     EXHIBIT 5.1
                               September 26, 1997


Board of Directors
Bioanalytical Systems, Inc.
2701 Kent Avenue
West Lafayette, IN 47906

     Gentlemen/and Mrs. Kissinger:

     We have acted as counsel to Bioanalytical Systems, Inc., an Indiana
corporation (the "Company"), in connection with the filing of a Registration
Statement on Form S-1 (the "Registration Statement") with the Securities and
Exchange Commission (the "Commission") for the purposes of registering under
the Securities Act of 1933, as amended (the "Securities Act"), an aggregate of
up to 1,725,000 Common Shares of the Company (the "Shares") which are to be
offered to the public.  Of the Shares, up to 225,000 Shares may be issued by
the Company to  cover the over-allotment option to be granted to the
underwriters.

     In connection therewith, we have investigated those questions of law we
have deemed necessary or appropriate for purposes of this opinion.  We have
also examined originals, or copies certified or otherwise identified to our
satisfaction, of those documents, corporate or other records, certificates and
other papers that we deemed necessary to examine for the purpose of this
opinion, including:

            1. The proposed form of Second Restated Articles of Incorporation
               of the Company.

            2. A proposed form of specimen certificate representing the Shares;
               and

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Board of Directors
September 23, 1997
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            3. The Registration Statement.

     For purposes of this opinion, we have assumed (i) that the Shares will be
issued pursuant to the terms of the Registration Statement; and (ii) that no 
changes will occur in the applicable law or the pertinent facts before the 
issuance of the Shares.

     Based upon the foregoing and subject to the qualifications set forth in
this letter, we are of the opinion that when (a) the Second Restated Articles of
Incorporation of the Company have been adopted and approved by the Board of
Directors and shareholders of the Company and filed with the Secretary of
State of the State of Indiana in the  manner contemplated by the Indiana
Business Corporation Law and the Registration Statement, (b) the pertinent
provisions of the  Securities Act and all relevant state securities laws have
been complied with and (c) the Shares have been delivered against payment
therefor as contemplated by the Registration Statement, the Shares will be
validly authorized, legally issued, fully paid and non-assessable.
        
     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this Firm under the caption
"Legal Matters" in the Prospectus included as a part of the Registration
Statement.  In giving this consent, we do not admit that we are within the
category of persons whose consent is required under Section 7 of the Securities
Act or under the rules and regulations relating thereto.



                                           Very truly yours,

                                          /s/ ICE MILLER DONADIO & RYAN