Thirty patients with suspected abnormality of the breasts on mammography were evaluated with magnetic resonance imaging (MRI) in a blind fashion. Spin-echo (SE) 250/30 msec scans were used to screen the examined breast. At the location of the suspected abnormality, inversion recovery (IR) 1000/30/300, SE 1000/30, and SE 1000/120 scans were performed. On the basis of these magnetic resonance images and experience with 70 previously studied patients, abnormalities of the breasts were grouped into five patterns. Ten malignant lesions exceeded 1 cm in diameter and were all correctly diagnosed by mammography and MRI. Of the remaining 20 benign conditions, four were suspicious for malignancy on MRI compared to eight with mammography. The shape of the lesion and the change in its signal intensity with different MR radiofrequency pulse sequences allows differentiation between a benign and a malignant process. On the basis of this preliminary experience, it seems MRI may have an adjunctive role to screening mammography. SE 1000/120 scans show higher signal intensity from carcinoma than from normal duct tissue, fibrocystic disease, and fibroadenoma. In this respect, it may allow some tissue specification in the breast.