Radionuclide bone scanning is a well-established technique for the investigation of suspected metastatic disease to bone. Most commonly, primary cancers of breast, prostate, and lung tend to metastasize to the skeleton. Current topics on the role of bone scanning in patients with these conditions are reviewed. Despite the now known sensitivity of MR imaging for the detection of bone marrow involvement, bone scanning continues to be the methodology of choice in view of its simplicity, low cost, and ability to screen the whole body. Tumor markers such as prostate-specific antigens have a new role in the investigation of metastasis arising from prostate carcinoma; this area is also reviewed. Although bone-seeking radionuclide tracers have, on the whole, remained unchanged from a diagnostic point of view, new bone-seeking tracers have been developed for the treatment of unremitting pain in patients with multiple secondary tumors to the skeleton. This new area appears particularly promising and will widen the scope of the radionuclide tracer method as a therapeutic modality. Single-photon emission CT is helpful in improving the more exact localization of areas of increased tracer uptake in the skeleton and is therefore more often used as an imaging methodology.