Magnetic resonance imaging (MRI) is evolving as a particularly valuable diagnostic procedure in the evaluation of musculoskeletal pathology. To assess the role of MRI as applied to the shoulder, we examined eight normal volunteers, six patients with seven arthrographically proven rotator cuff tears and two patients with impingement symptomatology but with negative double contrast conventional and computed tomographic arthrography. The studies were performed on a 1-Tesla magnet operating at 0.5 Tesla. Coronal T1-weighted images were obtained in all cases and coronal spin density and T2-weighted pulse sequences were employed in two cases. In the normal individuals, the supraspinatus muscle and tendon could be consistently demonstrated. The proximal humeral marrow, the superior glenoid labrum, and the acromioclavicular joint could also be examined. Findings in patients with rotator cuff tears included: (1) hypointense gap within the supraspinatus muscle-tendon complex on T1-weighted sequences, (2) absence of a demonstrable supraspinatus tendon with narrowing of the subacromial space secondary to elevation of the humeral head, and (3) increased signal within the supraspinatus tendon on T2-weighted images. In the patients with impingement syndrome and negative arthrography, MR demonstrated elevation of the supraspinatus tendon with subacromial impingement in one case and a normal supraspinatus tendon in the other. Impingement on the coracoacroaminal arch causes progressive fibrosis, atrophy, and eventual tear of the rotator cuff. The potential applications of MRI relative to the shoulder include assessment of tendon retraction in patients with supraspinatus tears and noninvasive evaluation of patients with impingement syndrome, permitting etiologic determinations, hopefully before irreversible tendon injury has occurred.