To verify the usefulness of 99mTc tetrofosmin scintigraphy in the follow-up of breast cancer patients, we studied 72 surgically treated breast cancer patients with suspected local recurrences (20 cases) or distant metastases (52 cases) at clinical examination and/or at conventional imaging procedures (CIPs). In all patients, a whole-body scan followed by planar and single photon emission tomography (SPET) images of selected sites were acquired 10 min after the intravenous injection of 740 MBq of 99mTc tetrofosmin, using a rectangular dual-head gamma camera equipped with high-resolution parallel-hole collimators. Loco-regional recurrences were diagnosed in 19 patients and distant metastases in 44 cases, while benign lesions were ascertained in nine cases. 99mTc tetrofosmin SPET showed higher sensitivity, specificity and accuracy per patient than did CIP (96.8% vs 85%, 77.7% vs 55.5% and 94.4% vs 81.1%, respectively) with statistical significance for accuracy (P <0.05). The combined use of SPET and CIP achieved 100% sensitivity and 98.6% accuracy. Planar imaging did not give additional information in respect of either SPET or CIP, showing significantly lower sensitivity and accuracy values (47.6% and 52.8%, respectively). Our data seem to suggest that 99mTc tetrofosmin SPET, but not planar, may be useful in the follow-up for the detection of loco-regional and distant recurrences in patients with breast cancer. The technique can play a complementary role to conventional diagnostic imaging procedures in selected patients.