Since modern medical, surgical, and radiation therapy in bony lesions are both specific and complex, as well as having associated risks, tissue diagnosis has been become even more important. Because open surgical biopsy has greater morbidity, takes a longer time to perform, may delay institution of therapy, and is more expensive, closed biopsy techniques have become popular. Between July 1991 and April 1994, 91 percutaneous needle bone biopsies were performed at the Department of Orthopedic Surgery and the Department of Radiology of Seoul National University Hospital. Fluoroscopy guided needle bone biopsies were performed in 81 cases and computerized tomography guided needle bone biopsies in 10 cases. To assess the diagnostic yield, the accuracy of diagnoses, the adequacy of sampling, the incidence of complications associated with the biopsy procedure, we analyzed these 91 percutaneous bone biopsies retrospectively. Ninty-one cases composed of 25 primary malignant bone tumors, 28 metastatic bone tumors, 20 benign bone tumors, 12 infections and 6 miscellaneous bone disorders. The number of cases in which adequate samples for histologic diagnosis were acquired(the adequacy of sampling) was 80(88%) and the number of inadequate samples was 11(12%). The overall diagnostic yield and diagnostic accuracy were 80%, 91% respectively. There was no complication in all cases. In conclusion, percutaneous needle bone biopsy may be a yielding, useful and safe diagnostic tool in bony lesions.