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                                   EXHIBIT 5.1

                             [Ice Miller letterhead]





April 21, 2003

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

Gentlemen:

      We have acted as counsel to Bioanalytical Systems, Inc., an Indiana
corporation (the "Company"), in connection with the registration of 228,856
common shares (the "Shares"), covered by the Registration Statement (together
with all amendments thereto, the "Registration Statement"), under the Securities
Act of 1933, as amended (the "1933 Act") including the information
statement/prospectus contained in the Registration Statement (as amended or
supplemented, the "Prospectus") that the Company is filing in connection with
the proposed merger of Pharmakinetics Laboratories, Inc., a Delaware
corporation, into PI Acquisition Corp., a wholly owned subsidiary of the Company
(the "Merger"). Unless otherwise defined herein, capitalized terms used shall
have the meaning assigned to them in the Registration Statement.

      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  Registration  Statement,  including  the  form of  prospectus
included therein,  in the form in which has been filed with the Securities and
Exchange Commission under the 1933 Act;

      2.    A copy of the Company's  Restatement of Articles of  Incorporation
certified by the  Secretary of State of Indiana on September  11, 2002 to be a
true and correct copy thereof;

      3.    A copy of the  Amended  and  Restated  Bylaws of the  Company,  as
amended to date;

      4.    Resolutions  relating  to the  approval  of  the  Merger  and  the
approval of the issuance and  registration of the Shares and the filing of the
Registration   Statement   adopted  by  the   Company's   Board  of  Directors
(collectively, the "Resolutions");

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Board of Directors
Bioanalytical Systems, Inc.
April 21, 2003
Page 2


      5. Such other documents and matters as we have deemed necessary or
appropriate to express the opinion set forth in this letter, subject to the
assumptions, limitations and qualifications stated herein.

      We have also relied, without investigation as to the accuracy thereof, on
other certificates of and oral and written communication from public officials
and officers of the Company.

      For purposes of this opinion, (i) we have assumed the authenticity of all
documents submitted to us as originals and the conformity to authentic originals
of all documents submitted to us as certified or photostatic copies; and (ii) we
have relied upon a certificate from an officer of the Company stating that the
Resolutions have not been amended, altered or superseded as of the date hereof.

      Based upon the foregoing and subject to the qualifications set forth in
this letter, we are of the opinion that the Shares are duly authorized and, when
issued and delivered in accordance with the resolutions of the Board of
Directors authorizing their issuance and the terms of the Merger as summarized
in the Prospectus, will be validly issued, fully paid and nonassessable.

      We consent to the use of this opinion as an exhibit to the Registration
Statement, to the disclosure and summarization of the opinion in the
Registration Statement, including in the Prospectus, and to the reference to our
firm in the Registration Statement under the caption "Legal Matters." In giving
this 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,
as amended, or the rules and regulations of the Securities and Exchange
Commission promulgated thereunder.

                                    Very truly yours,



                                    /s/ ICE MILLER