PURPOSE: To describe clinical and pathologic characteristics and outcome of patients with renal sarcomas. PATIENTS/METHODS: The IRSG database includes newly diagnosed patients (RMS) or undifferentiated sarcoma (UDS). We identified patients with renal sarcoma and reviewed their charts. RESULTS: Ten of the 5,746 eligible IRSG patients enrolled from 1972 to 2005 had primary renal embryonal RMS (N = 6) or UDS (N = 4). Anaplasia was present in six (60%) of the tumors. Patients' ages ranged from 2.6 to 17.8 years. Tumor diameters ranged from 7 to 15 cm (median, 12 cm). At diagnosis, seven patients had localized disease: four underwent complete removal of tumor (Group I), two had microscopic residual (Group II), and one had gross residual tumor (Group III). Three patients had distant metastases (Group IV) in lungs and bone. Nine patients received vincristine, actinomycin D and cyclophosphamide (VAC). Two Group I patients received no radiation therapy (XRT); others received XRT to the primary tumor and to some metastatic sites. Nine patients achieved complete disappearance of tumor, six due to the initial operation. Tumors recurred in lung (N = 2) or brain (N = 1) in Group IV patients; each died within 16 months. The Group III patient died of Aspergillus pneumonia. The six Group I and II patients survive, continuously disease-free, at 2.7-17.3 years (median, 4.7 years). CONCLUSIONS: Patients with renal sarcomas often present with large tumors, many of them containing anaplastic features. Removing all gross disease at diagnosis, if feasible, is a critical component of treatment to curing patients with renal sarcoma.