Sarcomas of the pelvic girdle represent difficult treatment problems. Many are not treatable for cure, and among the patients who are technically resectable, there is high risk for local tumor recurrence and distant spread. Intraoperative radiotherapy (IORT) has been used in conjunction with surgical resection in five patients with extensive sarcomas of the pelvic girdle. Patients underwent a hemipelvectomy and IORT (dose 20-30 Gy) to the sacral resection margin and surrounding soft tissues. Three patients developed pulmonary metastases within 3 months and eventually died from metastatic disease (8-38 months). Two patients have remained disease-free (43 and 53 months). Four patients (80%) have remained locally free of tumor with follow-ups of 8-53 months. The only treatment complication was late osteonecrosis of the coccyx which appeared 7 months after treatment. By contrast, six historical control patients with sarcomas of the pelvic girdle treated with resection alone showed a local control rate of only 27% over a 40-month follow-up. On the basis of this preliminary experience, it appears that IORT may substantially help to control local disease in patients with grossly resectable sarcomas of the bony pelvis.