Percutaneous biopsy of lytic lesions of the bone, in the past pertaining to orthopedic surgeons, has now become a part of interventional radiology. Fluoroscopic guidance has simplified its execution. US does not, under normal conditions, allow an accurate examination of the skeleton; on the other hand, when the bone tissue is replaced by soft tissue, US can easily demonstrate the presence of a tumefaction, caused by a lytic lesion, and determine its characteristics. Eleven patients with lytic lesions (recognized on plain film) underwent US. The lesions were demonstrated. In such cases, biopsy is essential to define their benign or malignant nature, in the latter case if primitive or metastatic, and their histology as well. US is a simple guide to the biopsy of noncorticalized lytic lesions, and it offers consistent advantages over fluoroscopic guidance--i.e. it is easier to perform, it requires no X-ray exposure, it provides with three-dimensional images, the guide is performed in real time, and a choice of the most appropriate (non-necrotic) areas is possible.