Patients undergoing bone scintigraphy or about to have breast surgery were studied with either 99mTc-polyphosphate or 99mTc-diphosphonate. Seven of 8 patients with carcinoma demonstrated a focal area of increased uptake. The 9 controls, who were clinically free of breast disease, had normal images. In the benign group, increased uptake was seen in patients with gynecomastia, lactating breasts, or acute inflammation. Most patients showed correlation with mammography and thermography.