The lysozyme (muramidase) activity was measured in the sera of 84 dogs with neoplastic disease. Neoplasms included 32 lymphomas, 13 primary bone neoplasms, 5 melanomas, 5 thyroid neoplasms, 9 soft tissue sarcomas, 5 mast cell sarcomas, and 15 carcinomas. The sera from 21 healthy dogs served as