A review of 120 percutaneous bone biopsies performed on 110 patients in the Radiology Department of the Hospital for Special Surgery showed a 72% concurrence of biopsy findings with the patient's other clinical findings and subsequent course. Of the biopsies, 58% were correctly positive for malignancy or infection and 14% were correctly negative. The rest, 28% of the biopsies, were either incorrectly negative or had insufficient tissue for diagnosis and were therefore unsatisfactory. Only eight positive cultures from biopsy material were obtained in 21 cases with bone infections. In diagnosing metastasis, a higher success rate (84%) was noted in vertebral biopsies than other sites (66%). Poor success (44%) was noted, however, in biopsying primary bone neoplasm.