Bone scans with Tc + 99m phosphate were performed in 87 patients with histological diagnosis of breast cancer, in order to evaluate whether this technique was suitable in detecting small metastasis both at first staging and in follow-up. The scans were considered as: a) "malignant", when an isotope uptake in usually inactive sites and/or an increased uptake in normally active areas were demonstrated; b) "equivocal", when the uptake in normally inactive and/or in normally active sites was only moderately increased; c) "benign", when only slight uptake increase in normally active structures was detectable. The scans have been carried out before or soon after mastectomy (early scans), and repeated at 6 month intervals (N+ patients and/or malignant or equivocal scans) or at 12 month intervals. A significantly greater incidence of malignant scans was observed in stages 2 and 3 as compared to stage 1, and in stage 4 as compared to all the other stages, as well as in premenopause versus postmenopause patients.