ICRF-159 is active in several animal tumor model systems and human adult malignancies. In this phase II study, ICRF-159 was given on a weekly schedule, 3000 mg/m2/day, orally in three divided doses at 6-hour intervals to 78 children with a variety of malignant neoplasms. Fifty-three patients were evaluable for tumor response. Toxicity was primarily hematopoietic and gastrointestinal. There were no responses in any of the eight patients with osteogenic sarcoma, four with lymphoma, five with Ewing's sarcoma, ten with neuroblastoma, or six with rhabdomyosarcoma. There was a transient partial response in one of four children with Wilms' tumor. Further trials with this drug using this schedule are not indicated for the common childhood solid tumors.