51 patients suffering from 125 bone metastases of various primary tumors were investigated with three-phase skeletal scintigraphy in an attempt to define criteria characteristic for bone metastases with regard to differential diagnosis. During the 3 phases of imaging, the metastases exhibited 5 different patterns of activity concentration. None of these patterns was correlated either to the size and morphological X-ray appearance of the metastases or to the histology of the primary tumors. The intensity of radionuclide concentration was also varying. The most frequent patterns of activity concentration were increased uptake during the blood-pool phase and skeletal phase combined with absence of concentration during the angiographical phase (43%), and increased uptake during all of the 3 phases (34%). In this series, a pattern of scintigraphical findings characteristic for bone metastases or helpful in the differential diagnosis could not be determined. In our experience, three-phase skeletal scintigraphy is not useful in the diagnosis and differential diagnosis of bone metastases.