A phase II trial was conducted to determine the clinical activity of amsacrine (m-AMSA) in patients with heavily pretreated solid tumors, myeloma, and lymphoma at the University of Arizona Cancer Center. Additionally, m-AMSA was evaluated at other Southwest Oncology Group institutions in breast cancer, myeloma, melanoma, and oat cell cancer of the lung. At a dose of 120 mg/m2 given iv every 28 days, 12 partial responses were observed in 221 patients evaluable for response. Some antitumor activity was observed in breast cancer (four responses of 65 patients), non-Hodgkin's lymphoma (three of nine), Hodgkin's disease (two of five), and sarcoma (two of 15). A partial response was also documented in one of two patients with cervical cancer. Among the 135 patients treated at the University of Arizona who were extensively evaluated for toxic effects, only myelosuppression and anemia were seen in a significant number of patients. At this dose and schedule, 29% of patients developed leukopenia of less than 3000 cells/mm3, 16% developed a thrombocytopenia of less than 100,000 cells/mm3, and 29% had an acute fall in hemoglobin of greater than or equal to 2 g/100 ml. In addition, two patients suffered grand mal seizures which were not clearly drug-related. These results suggest that further study of m-AMSA in lymphoma, sarcoma, and cervical cancer is warranted.