The glenohumeral joint is the most mobile articulation in the body and the most commonly dislocated diarthroidal joint. Anterior dislocation is by far the most common direction and can lead to instability of the glenohumeral joint, which ranges from subtle increased laxity to recurrent dislocation. Overtime, understanding of anterior shoulder dislocations and the resulting instability has improved. Likewise, significant advances in arthroscopic equipment have allowed use of the arthroscope to address anatomically the various lesions that cause instability. This article reviews the anatomy, pathophysiology, clinical evaluation, and treatment of anterior shoulder instability.