Forty-five immunocompetent patients with solid tumors were immunized with BCG, PPD, and tumor cells. The methods were practical, but the morbidity was significant, including painful draining ulcerations at vaccine sites, possible enhancement of tumor growth in three patients, and the discovery at autopsy of systemic tuberculosis in one patient. Various facets of cellular immunity were altered, namely: 1) a majority of the patients developed enhanced cutaneous reactions to the microbial skin-test antigens (particularly tuberculin) and tumor cells; 2) nine patients developed the equivalent of delayed hypersensitivity reactions or flares at all previous PPD and BCG inoculation sites following subsequent injection of these agents, which supports the concept of immunologic memory for these target antigens; 3) lesions resembling those of "spontaneous" regressed moles (halo-nevi) were observed at previous vaccine sites in 20 patients and generalized depigmentation occurred in three patients; 4) foreign body giant cells in tumor metastasis remote from BCG-PPD-tumor vaccine sites may indicate a cross-reactivity of microbial and tumor antigens; and 5) intralesional inoculation of the nonspecific agents (BCG, PPD, Varidase, and Mumps) resulted in dense mononuclear cell infiltration and complete regression of most of the injected lesions. Destruction of single or multiple lesions by local injections of antigens did not provide either significant regression of uninjected lesions or clinical benefit.