1 EXHIBIT 21 SUBSIDIARIES OF REGISTRANT Stericycle of Arkansas, Inc., an Arkansas corporation Stericycle of Washington, Inc., a Washington corporation SWD Acquisition Corp., a Delaware corporation Environmental Control Co., Inc., a New York corporation Waste Systems, Inc., a Delaware corporation 3CI Complete Compliance Corporation, a Delaware corporation Med-Tech Environmental Limited, an Ontario (Canada) corporation Med-Tech Environmental (CDA), Ltd., a federal Canadian corporation Bio-Med Waste Disposal Systems, Ltd., an Ontario (Canada) corporation Med-Tech Environmental, Inc., a Delaware corporation Med-Tech Environmental (MA), Inc., a Delaware corporation 507375 N.B. Ltd., a New Brunswick (Canada) corporation