Extracranial neoplasms were visualized by scintiscanning as a result of Tc99m pertechnetate concentration within them. Seventeen of the 26 known neoplasms scanned were demonstrated, and the compound seems worthy of further investigation. Pertechnetate as a scanning agent has the intrinsic advantages of immediate and rapid scanning and relatively low patient irradiation. However, it has the limitation of marked activity in normal blood pools and some normal organs, as well as in certain non-neoplastic lesions.