JOINT FILING AGREEMENT

                                    Exhibit A

                             JOINT FILING AGREEMENT

         In accordance with Rule 13d-1(f) under the Securities Exchange Act of
1934, as amended, the undersigned hereby agree to the joint filing on behalf of
each of them of a statement on Schedule 13D (including amendments thereto) with
respect to the Common Stock, $.01 par value, of BioWhittaker, Inc., and that
this Agreement be included as an Exhibit to such joint filing. This Agreement
may be executed in any number of counterparts all of which taken together shall
constitute one and the same instrument.

         IN WITNESS WHEREOF, the undersigned hereby execute this Agreement this
2nd day of October, 1997.

                                        /s/ Xxxxxxx Xxxxxxx
                                        Xxxxxxx Xxxxxxx


                                        /s/ Xxxxxxx X. Xxxxxxx
                                        Xxxxxxx X. Xxxxxxx


                                        /s/ Xxxx X. Xxxxxxx
                                        Xxxx X. Xxxxxxx


                                        XXXXXX XXXXXXX & CO., INC.

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            Xxxxxxx Xxxxxxx
                                            Chairman and Chief Executive Officer


                                        MSC PARTNERS, L.P.
                                        By: Xxxxxxx Management, Inc.
                                            General Partner

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            Xxxxxxx Xxxxxxx
                                            President



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                                        XXXXXXX MANAGEMENT, INC.


                                        By: /s/ Xxxxxxx Xxxxxxx
                                            Xxxxxxx Xxxxxxx
                                            President


                                        XXXXXXX OFFSHORE, L.L.C.


                                        By: /s/ Xxxxxxx Xxxxxxx
                                            Xxxxxxx Xxxxxxx
                                            Managing Member


                                        XXXXXXX FUND, INC.


                                        By: /s/ Xxxxxxx Xxxxxxx
                                            Xxxxxxx Xxxxxxx
                                            President



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