1. At an operation for recurrent posterior dislocation of the shoulder observations were made on the mechanism, head defect, method of reduction, and the position of greatest stability.

2. Experimentally, avulsion of the glenoid labrum in a monkey was shown to be capable of sound repair without operation.

3. In the treatment of primary posterior dislocation it is suggested that the position of abduction, lateral rotation and extension is favourable for the approximation of the stripped labrum and capsule to the glenoid rim, and for an effective buttress after cicatrisation.

4. If the risk of recurrence is to be reduced to a minimum the shoulder should be retained in the position of greatest stability for at least four weeks, to allow firm union of the avulsed soft tissues.

5. This position for an optimum buttress would also apply after surgical repair for recurrent posterior dislocation.