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                                                                     EXHIBIT 2.2

                               FIRST AMENDMENT TO

                            ASSET PURCHASE AGREEMENT



         This First Amendment (the "Amendment") is entered into as of October
22, 1999 by Allied Waste Industries, Inc., a Delaware corporation ("Seller"),
and Stericycle, Inc., a Delaware corporation ("Buyer").

                                    Recitals

         A. Seller and Buyer are parties to an Asset Purchase Agreement dated as
of April 14, 1999 (the "Asset Purchase Agreement"), pursuant to which Seller has
agreed to sell and Buyer has agreed to purchase the BFI Canadian Medical Waste
Operations.

         B. Seller and Buyer desire to amend the Asset Purchase Agreement as
provided in this Amendment pursuant to the terms of Section 9.7(a) of the Asset
Purchase Agreement.

         Now, therefore, in consideration of their mutual promises, the parties
agree as follows:

         1. DELETION OF CERTAIN PROVISIONS. Sections 1.3 and 1.5 of the Asset
Purchase Agreement are deleted in their entirety, so that the sole possible
adjustment to the Purchase Price under the Asset Purchase Agreement is the
adjustment for working capital set forth in Section 1.4.

         2. AMENDMENT OF SECTION 1.4(a).  The following sentence is added at
the end of Section 1.4(a) of the Asset Purchase Agreement:

         To facilitate Buyer's collection of the accounts receivable of the
         Business, Seller shall cause control to be transferred to Buyer at the
         Closing of all lock boxes used exclusively by customers of the Business
         to remit payments.

         3. CAPITALIZED TERMS. Capitalized terms used but not otherwise defined
in this Amendment have the same meanings that they have in the Stock Purchase
Agreement.

         4. CONTINUING EFFECT. Except as amended by this Amendment, all of the
terms and provisions of the Stock Purchase Agreement shall remain in full force
and effect.

         5. EXECUTION IN COUNTERPARTS. This Amendment may be executed in any
number of counterparts, each of which shall be deemed an original.

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         In witness whereof, the parties have cause this Amendment to be duly
executed as of the day and year first written above.


                                  ALLIED WASTE INDUSTRIES, INC.


                                  By:     /s/ Thomas H. Van Wheelden
                                       -----------------------------------------
                                  Name:   Thomas H. Van Wheelden
                                  Title:  Chairman of the Board of Directors,
                                          President and Chief Executive Officer



                                  STERICYCLE, INC.


                                  By:     /s/ Mark C. Miller
                                       -----------------------------------------
                                  Name:   Mark C. Miller
                                  Title:  President and Chief Executive Officer






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