Posterior shoulder dislocation resulting in instability (PSI) is an increasingly recognized disease entity in young active individuals. Although rare in the general population compared to anterior instability, the prevalence of PSI has been reported to be up to 24% in young athletes participating in sports, climbers, and weightlifters. Concomitant bone loss, reverse Hill-Sachs lesions, and soft tissue pathology result in articular surface incongruence that alters the functional biomechanics of the shoulder. Diagnosis may be difficult for the untrained specialist and is often missed in routine emergency visits. Delayed diagnosis contributes to the significant morbidity associated with posterior glenohumeral instability/dislocations with bone loss. This chapter will review the etiology and pathomechanics of PSI, clinical and diagnostic evaluation, radiographic assessment of bone loss, and a personalized approach to successful intervention. The advantages, disadvantages, and outcomes of nonoperative and operative treatments including closed reduction and appropriate rehabilitation, posterior labral repair with and without bone augmentation or reconstruction of a reverse Hill-Sachs lesion, autologous or allogenic bone and tissue transfer, consideration of rotator interval closure, role of osteotomy (rotational humeral/glenoid) in patients with chronic pathology, glenoplasty, prosthetic replacement, and innovative procedures such as percutaneous balloon humeroplasty will be reviewed.