Bone scans using 99mTc polyphosphate have been obtained in 174 patients with newly diagnosed carcinoma of the breast. This number represents 68 per cent of all patients registered with the disease in northern Alberta during the 12 months of the study. In nine patients, the roentgenograms were abnormal, but in 18, there was scintiscan evidence of metastatic disease involving bone, although one false-negative interpretation is included in this number. In another eight patients with normal or equivocal initial bone scintiscans, metastatic disease involving bone developed during a 12 months' period of observation.