Fifty children with clinical group III (localized, but unresected) or clinical group IV (disseminated) soft tissue sarcomas were entered in a trial to determine if the addition of etoposide and cisplatin to standard chemotherapy regimens and irradiation (4,000 cGy) would be tolerated by pediatric patients. Responding patients had a secondary surgical procedure performed after approximately 20 weeks of therapy for the purpose of establishing histological response, determining its extent, and removing residual tumor tissue, when feasible. Such procedures were performed in 29 of 50 (58%) of these patients, ie, 20 of 31 (65%) of those in group III, and nine of 19 (47%) of those in group IV. Surgical procedures consisted of exploration of the site and biopsy (only) in 16 patients; grossly complete tumor excision in nine; and subtotal tumor excision in four. In nine patients (six in group III, three in group IV) apparent total excision of a previously unresected primary tumor mass was accomplished at second surgery. One distant but no local relapse has occurred in this group, and eight of nine have survived (five of six with identified tumor in the specimen) for a duration of 232 to 348 weeks (six greater than 260 wks), suggesting that among patients with primary tumors in selected sites, with either stage III or stage IV disease, excision of residual masses following intensive chemotherapy/radiotherapy regimens may favorably influence outcome. Local relapse subsequently occurred in seven of 18 patients in whom tumor tissue could not be identified in biopsy specimens or in excised masses taken from the primary site at second surgery.(ABSTRACT TRUNCATED AT 250 WORDS)