From January, 1970 until December, 1987, a total of 188 malignant melanoma lesions in 92 patients were treated at the Department of Radiation Oncology, Indiana University Medical Center, Indianapolis, Indiana. Response was evaluated in 181 evaluable lesions treated by radiation alone and radiation plus hyperthermia to assess differences in response to a total dose, dose per fraction and overall time of treatment, as well as effects of adjunctive hyperthermia treatment. Different fractions of radiation, ranging from 100 cGy to 1000 cGy, were used. Local hyperthermia was administered for one hour following radiation treatment using microwave with different frequencies. The tumor temperature was also monitored during treatment. With a radiation dose of less than 400 cGy per fraction, and complete response rate (CR) was 34% (16/47) and the objective response rate (OR) was 62% (29/47). When hyperthermia was added, the complete response rate rose from 34% to 70%. With a dose of more than 400 cGy per fraction, the CR was 63% (48/77), and OR was 95% (73/77). When hyperthermia was added, the complete response rate rose from 63% to 77%.