The oncologic outcome in the treatment of pelvic sarcomas is not comparable with that in the extremity. Particular problems arise when the tumor involves the posterior pelvis and the sacrum or even the lower lumbar spine. Because of the difficulty in achieving local control and the major functional deficits after extensive surgery, some authors suggest conservative, nonsurgical treatment for these patients. The purpose of the current study was to analyze the oncologic outcome of patients who were treated for a pelvic sarcoma necessitating resection of the ilium, part of the sacrum and part of the lower spine, which is defined as extended hemipelvectomy. Between 1979 and 1999, 11 males and seven females with a mean age of 34.5 years (range, 14-67 years) had an extended hemipelvectomy for a sarcoma of the posterior pelvis. The tumors included seven osteogenic sarcomas, six chondrosarcomas, and five fibrosarcomas: 13 were classified as high-grade lesions. The mean size of the tumor was 11 x 9 x 6 cm. In 11 patients, a hemivertebrectomy of L5 and in seven patients of L4 combined with L5 was done to achieve an adequate margin. In four patients, the resection was followed by reconstruction with a vascularized fibula or autograft. At a mean followup of 56 months (range, 3-220 months), 12 of 18 patients were alive and without disease. Six patients died; four of these patients had metastasis to the lung at presentation. The two remaining patients died of complications of adjuvant treatment. The authors conclude from this small series of patients that an aggressive surgical resection for localized, nonmetastatic, high-grade sarcomas of the posterior pelvis may be justified to provide local control and improve survival.