Twenty-four patients who had posterior subluxation of the glenohumeral joint were assigned to one of two groups on the basis of the severity of the symptoms. The sixteen patients in Group I, who had less severe symptoms, were treated with a physical therapy program that was based on exercises to strengthen muscles. The eleven patients in Group II (three of whom had no success with physical therapy when they were originally in Group I) had a posterior capsulorrhaphy, with or without a bone block. According to an over-all rating, Group I had a rate of success of 63 per cent, and Group II had a rate of success of 91 per cent. The patients who had more severe ligamentous laxity were not more likely to fail either of the treatment programs. Although voluntary subluxation may be a subtle but important indicator of underlying emotional difficulties, it appears that, in the patient who is emotionally stable, the ability to voluntarily subluxate the shoulder posteriorly is not associated with a negative prognosis for either non-surgical or surgical treatment. Patients who have moderately disabling posterior subluxation of the shoulder should be treated with an intensive program that is designed to strengthen muscles. Patients who have symptoms that are severely disabling or who have had no success with non-operative treatment should be treated with posterior capsulorrhaphy. When the posterior aspect of the glenoid is severely deficient and when the posterior portion of the capsule or the infraspinatus tendon is attenuated, a bone block should augment the reconstruction.