<Page> EXHIBIT 21 CANTEL MEDICAL CORP. SUBSIDIARIES OF REGISTRANT -------------------------------- Carsen Group Inc. (Amalgamated under the laws of Ontario, Canada) Minntech Corporation (Incorporated under the laws of Minnesota) Minntech B.V. (Incorporated under the laws of The Netherlands) Minntech Japan K.K. (Incorporated under the laws of Japan) Biolab Equipment Atlantic Ltd. (Incorporated under the laws of Pennsylvania) Biolab Equipment Ltd. (Incorporated under the laws of Canada) Biolab Equipment Canada Ltd. (Incorporated under the laws of Canada) Biolab Equipment Quebec Ltd. (Incorporated under the laws of Canada) Mar Cor Services, Inc. (Incorporated under the laws of Pennsylvania)