Subglenoid dislocation of the shoulder is uncommon. The clinical picture is striking and the radiographic appearances are characteristic, with the head of the humerus lying inferior to the glenoid and the shaft directed upwards and internally rotated. Complications such as associated fractures and injury to the brachial plexus or acillary vessels may occur. Fracture of the greater tuberosity or rupture of the rotator cuff is always seen. Post-traumatic frozen shoulder is common and leads to a poor functional result. The authors describe ten cases and review the literature. The mechanism of the injury is discussed and experimental evidence which supports the current concepts of shoulder instability is reviewed.