Cis-Dichlorodiammineplatinum(II) (DDP) was studied in 16 children with advanced malignancies. Three dosage schedules were tried: regimen A, 20 mg/m2/day .times. 5 days for 3-4 wk (11 patients); regimen B, 50 mg/m2 once a week (4 patients) and regimen C, 60 mg/m2/day .times. 2 days every 3-4 wk (1 patient). Four of 16 patients (25%) showed partial response, including 1 with osteogenic sarcoma, 1 with neuroblastoma, 1 with seminoma and 1 with medullary carcinoma of the thyroid. Two patients showed clinical improvement. The major toxic manifestations included nausea and vomiting (16), renal toxicity (3 of 16), transient pancytopenia (6 of 12) and hearing loss (2 of 16). DDP has activity in pediatric tumors. A more precise response rate must be delineated in a larger series of patients.