The purpose of this study was to determine operability in malignant cases by proving the presence or absence of skeletal metastases. Radiographic findings have frequently led to error. Benign bone lesions sometimes resemble metastases, or extensive metastases may be present in bones which appear radiographically normal. The most frequent sites of bone metastases are the vertebral bodies. They are involved in from 50% to 75% of cases of carcinoma of the breast, lungs, and prostate. New instruments for biopsy of vertebral bodies were invented. Their use is described. In this study on the living, metastases were found in 20%. The fact that in the majority of cases bone biopsy was done before the metastatic spread was far advanced explains this low incidence.