Sixty-four children with primary rhabdomyosarcoma of the bladder or prostate were enrolled in the IRS during the initial five years (October 1972-November 1977). Observation of these patients for from 2 1/2-8 years forms the basis of this report. The chemotherapy-radiotherapy regimens employed (IRS) for each Clinical Group were: (1) Group I (completely excised tumor), sequential actinomycin-D (ACD), vincristine (VCN), and cyclophosphamide (CYP), i.e., standard (VAC), with or without radiotherapy (RT); (2) Group II (resected local disease with node involvement, "microscopic" residual, or local extension), RT plus sequential ACD and VCN, or RT plus standard VAC; (3) Group III, (gross residual disease); and (4) Group IV (dissemination), RT and either pulse VAC or pulse VAC plus Adriamycin (ADR). Pulse VAC consisted of VCN (day 1), plus daily intravenous ACD and CYP (days 1-5). Relapse rates were: Group I, 0/8; Group II, 6/23; and the mortality in Group III, 6/23; and in Group IV, 7/10. Among patients with bladder tumors, the rate of relapse was 2/11 following pelvic exenteration (anterior, 10; total 1); 5/12 following partial cystectomy or gross tumor excision; and 3/5 following a primary chemotherapy-radiotherapy (PCR) regimen. In patients with prostatic tumors (Groups I-III), relapse occurred in 0/14 patients treated initially by pelvic exenteration (anterior, 12; total, 2); and in 2/11 patients treated by a PCR regimen.