cis-Dichlorodiammineplatinum(II) (DDP) was studied in 16 children with far-advanced malignancies. Three dosage schedules were tried: regimen A, 20 mg/m2/day x 5 days for 3-4 weeks (11 patients); regimen B, 50 mg/m2 once a week (four patients); and regimen C, 60 mg/m2/day x 2 days every 3-4 weeks (one patient). Four of 16 patients (25%) showed partial response, including one with osteogenic sarcoma, one with neuroblastoma, one with seminoma, and one with medullary carcinoma of the thyroid. Two patients showed clinical improvement. The major toxic manifestations included nausea and vomiting (16 of 16), renal toxicity (three of 16), transient pancytopenia (six of 12), and hearing loss (two of 16). It is apparent that DDP has activity in pediatric tumors; however, a more precise response rate must be delineated in a larger series of patients.