Glenohumeral instability encompasses a spectrum of disorders of varying degree, direction, and etiology. The keys to accurate diagnosis are a thorough history and physical examination. Plain radiographs are frequently negative, especially in subtle forms of instability. Computed tomography (CT), CT arthrography, magnetic resonance imaging, arthroscopy, and examination under anesthesia may occasionally yield important diagnostic information. Nonoperative treatment of shoulder instability consists of reduction of the joint (when necessary), followed by immobilization and rehabilitative exercises. The length and the value of immobilization remain controversial. Rehabilitative programs emphasize strengthening f the dynamic stabilizers of the shoulder, particularly the rotator cuff muscles. Both arthroscopic and open techniques can be used for operative stabilization of the glenohumeral joint. Results of these repairs are assessed not only in terms of recurrence rate, but also in terms of functional criteria, including return to athletics. Some standard repairs have declined in popularity, giving way to procedures that directly address the pathology of detached or excessively lax capsular ligaments without distorting surrounding anatomy. Capsular repairs also allow correction of multiple components of instability.