Rubidazone was administered to 24 children with advanced solid tumors or leukemia. The dose ranged from 80 to 150 mg/m2/IV daily to a total dose of 160 to 450 mg/m2/course. This course was repeated at intervals of approximately three weeks. Eighteen of 24 patients (75%) had received adriamycin and daunomycin as part of prior chemotherapy. The major toxic effects observed were myelosuppression, nausea, vomiting, mucositis, and skin rash. Four patients developed abnormal echocardiograms following the rubidazone therapy, 2 manifested clinical cardiac failure, of which one had anthracycline cardiomyopathic changes on autopsy. One of 7 adequately treated ALL patients achieved M2 marrow and improved peripheral counts for 3 weeks. One of the 2 neuroblastoma patients had subjective improvement of bone pain for 2 months. Rubidazone, in a previous heavily treated group of patients used in this study, had dosages of 360 and 450 mg/m2 which produced marrow hyperplasia to aplasia, with only minimal responses.