Cine magnetic resonance imaging (MRI) was used to define the normal space between the humeral head and coracoid process, known as the subcoracoid space, to quantify the subcoracoid space in symptomatic patients and identify the anatomic structures responsible for narrowing of this space. The study population was comprised of 50 normal volunteers and 75 patients with shoulder pain. All subjects underwent cine MRI of the shoulder using a shoulder-rotating device that allows progressive rotation of the glenohumeral joint in 10 degrees increments from internal to external rotation while scanning the shoulder in the axial plane. In asymptomatic patients, the normal interval between the lesser tuberosity and coracoid process (coracohumeral distance) averaged 11 mm in maximum internal rotation. In symptomatic patients, impingement or entrapment of the subscapularis tendon and other soft-tissue structures between the lesser tuberosity and the coracoid process in internal rotation was identified, and the mean distance between the lesser tuberosity and coracoid process measured 5.5 mm in maximum internal rotation. This new MRI technique for shoulder imaging is safe, easy to perform, noninvasive, and well-tolerated by patients. Cine MRI provides valuable information on the subcoracoid region not obtainable with other methods.