One hundred fifty-three percutaneous bone biopsies were performed on 70 patients with and 83 patients without a known extraosseous primary tumor who had either scintigraphic evidence or plain radiographic evidence suggesting bony metastases. Biopsy results were shown to be true-negative, true-positive, or false-negative based on results of the needle biopsy, open biopsy, or radiographic follow-up. The overall accuracy of biopsy was 95.4%. In the group with positive scans only, the accuracy was 85.7%. Twenty-nine percent of the patients with known cancer and 33.7% of patients without cancer proved to have benign causes for their radiographic abnormality. The rate of significant complications was 0.7%. Biopsy of suspect osseous lesions can be performed safely and may significantly alter treatment. Biopsy of scan-positive, radiograph-negative lesions is a highly accurate procedure.