Inbred Sewall Wright strain 2 male guinea pigs with established intradermal tumors and microscopic lymph node metastases were treated either by local excision, cryosurgery, or intralesional injection of BCG. Cryosurgery and local excision were effective in eliminating growth of the primary tumor but failed to prevent growth of lymph node metastases. In contrast, intralesional injection of BCG caused regression of primary tumors and prevented growth of lymph node metastases.