Arthrotomography was used to study the glenoid labrum in 8 patients with problems of shoulder instability. In 4 patients an anterior lesion of the labrum was noted radiographically. The abnormality was confirmed at surgery in 3 of the 4. In 1 of the 3, anterior capsular detachment was also demonstrated radiographically and confirmed surgically. One patient had voluntary posterior subluxation: radiographically, the labrum was normal, and at surgery no abnormalities could be found. The technique, which is simple to perform, is described and radiographic anatomy discussed.