Among 154 children with primary vesical rhabdomyosarcoma entered in the IRS (1972 to 1986), tumor excision constituting a partial cystectomy was performed in 33. These procedures were performed in the following situations (1) as an initial operation for localized disease (22); (2) as a secondary procedure for localized disease following chemotherapy (CT) or CT/irradiation response (6); and (3) as an initial operation in the presence of disseminated abdominal disease (5). Partial cystectomy included full-thickness resection of 15% to 80% of the bladder wall. Ureters were reimplanted or revised in two patients. The 33 patients undergoing partial cystectomy were in the following clinical groups: I, total excision (10); II, gross excision with "microscopic residual" or positive nodes (8); III, subtotal excision (10); and IV, tumor dissemination (5). Patients in clinical groups I and II received vincristine and actinomycin-D (VA) or VA + cyclophosphamide (VAC) +/- adriamycin (ADR). Patients in groups III and IV received the same agents +/- cisplatin. Irradiation (2,000 to 5,000 cGy) was administered to 18 patients (55%) in groups II to IV. Six relapses occurred among 28 patients with localized disease, and one among five patients with dissemination; all resulting in progressive disease and/or death. Estimated 3-year survival following partial cystectomy (79%) is similar to that for all patients with primary bladder tumors (78%). In contrast with the total group, in which the majority of survivors have eventually required total cystectomy; 25 of 26 survivors of partial cystectomy have functional bladders from 146 to 686 weeks (median, 356 weeks) from study entry.(ABSTRACT TRUNCATED AT 250 WORDS)