The American College of Surgeons performed a patient care and evaluation study of malignant melanoma for years 1981 and 1987 to determine the presenting symptoms, methods of evaluation, clinical management, and disease outcome. Previous reports on malignant melanoma of the skin, mucous membrane, and eye have been published. This report details the findings for 58 patients with malignant melanoma of an unknown primary diagnosed in 1981 and 87 patients diagnosed in 1987. The total number of patients was relatively small in comparison to all malignant melanoma patients. These patients were younger than the skin, ocular, and mucous membrane melanoma patients. There were significantly more males than females. When the anatomical site of a pathological positive node was known, it most frequently was in the axilla. Surgery, radiation therapy, and chemotherapy were frequently used in treatment of these patients. Although the overall prognosis is poor, some patients will have long term survival, and aggressive therapy should be considered for at least some of these patients.