The optimal treatment of giant cell tumors of the pelvis and sacrum is controversial. Our current patient series was combined with cases identified in a review of the literature published in the past 50 years, yielding a combined group of 239 lesions for study. Recurrence rates were 49% for patients who had radiation therapy alone, 47% for patients who had surgery with intralesional margins, 46% for patients who had surgery with intralesional margins and radiation therapy, and 0% for patients who had surgery with wide margins. Six percent of patients had benign lung metastases develop, 2% of patients had secondary malignancies, 2% of patients died in the perioperative period, and less than 1% of patients had multicentricity. Radiation-induced sarcoma developed in 11% of patients who received radiation for primary or recurrent lesions. Larger doses of radiation therapy did not decrease the rate of local recurrence. Recurrence after surgery and radiation was not lower than after either treatment alone. Local recurrence was more likely in the patients with sacral tumors (48%) than in the patients with pelvic tumors (34%). Disease status was worse in the patients with sacral lesions (23% died of disease) than in the patients with pelvic lesions (6% died of disease).