This article reports on the diagnostic features, radiographic findings, staging, operative management, treatments, and treatment results for 95 children (mean age, 10 years) with paratesticular sarcoma; they were treated on the Intergroup Rhabdomyosarcoma Study (IRS) I and I1 protocols. Embryonal rhabdomyosarcoma (RMS) was the most common histologic subtype (97% of cases). Patients were randomly assigned to receive various therapeutic regimens according to IRS protocols. Among 81 patients (85%) with localized disease, most (57) were in Clinical Group I (localized, completely excised tumors), and 20 were in Group 11 (gross excision with tumor-involved, regional retroperitoneal lymph nodes or microscopic residual). Only four were in Group 111 (gross residual disease in the primary site or retroperitoneal lymph nodes). Three of them achieved a complete response (CR) after induction therapy and two then relapsed. The relapse-free survival (RFS) estimates at 3 years from diagnosis were 93% in Group I and 90% in Group 11. Distant metastases were present at diagnosis in only 14 patients. Twelve of them achieved CR, but four subsequently relapsed; their 3-year RFS estimate was 67%. Overall, survival rates among the 95 children were excellent (89% at 3 years) compared to the entire IRS series (63%). Treatment with radical orchidectomy and chemotherapy was sufficient for Group 1 patients. Orchidectomy, chemotherapy, and radiation therapy were highly effective in Group I1 patients and in a large proportion of those with more advanced tumors. Recommendations for the diagnostic examinations and management of future patients with paratesticular sarcoma are given.