BCG-CWS was administrated into lymphatic vessels in the treatment of advanced malignant melanoma metastasized to the lymph node of the posterior peritoneum. Side effects consisted of fever, lymphangitis, a decrease in urinary output and a slight rise in serum GOT, there being no serious side effects. Clinically, tumor mass in the abdomen cleared but metastases to the other organs increased, and the patient died of general dispersion of the disease. At autopsy, the abdominal mass became flat, with the cut surface of yellowish brown color. Histologically, this mass formed necrosis made up of destroyed tumor cells and histiocytes. BCG-CWS mediated histiocyte response appeared to destroy tumor cells. Thus, it is possible that local administration BCG-CWS could elicit a potent response even in advanced carcinoma. Since the contact of BCG-CWS with tumor cells produced this response, administration of BCG-CWS into the lymphatic vessels may be indicated where the lymph current to the metastasized lymph node is not obstructed. This treatment would be effective particularly in the case of micrometastasis, and there is a possibility that it could elicit a specific response.