This brief review of the more promising clinical trials suggests that immunotherapy is indeed beneficial for selected cancer patients. Because of its limited potency, it should not be used as primary treatment for malignant disease except as local immunotherapy for certain accessible tumors. It is effective for eradication of primary neoplasms of the skin as well as cutaneous metastases of malignant melanoma and breast carcinoma. The most important role for immunotherapy is in combination with other modalities. It may help control occult micrometastases that cause recurrence and death following surgical procedures or irradiation. Results of adjuvant immunotherapy appear promising for malignant melanoma, for carcinoma of the lung, breast, and colon, and for soft-tissue sarcomas. In combination with chemotherapy, immunotherapy appears to prolong remission and survival in acute myelogenous leukemia and in disseminated tumors of the lung and breast. Clearly, immunotherapy is not a panacea for malignant disease, but it could become an important arm in a multimodality attack on cancer.