In the clinical staging of malignancy, radionuclide bone scanning has played an increasingly important role. An area of increased radionuclide uptake on technetium 99 (99Tc) bone scan which is not visualized on skeletal radiographs can present a significant diagnostic dilemma. This can be further compounded by nonrevealing percutaneous or open surgical biopsies. The authors present a method of definitively localizing the appropriate site for bone biopsy in such circumstances. Use of this technique has allowed us to ascertain that isolated rib lesions in two patients with extra-osseous malignancies were not due to metastatic disease.