A specific pattern of injury to the superior labrum of the shoulder was identified arthroscopically in twenty-seven patients included in a retrospective review of more than 700 shoulder arthroscopies performed at our institution. The injury of the superior labrum begins posteriorly and extends anteriorly, stopping before or at the mid-glenoid notch and including the "anchor" of the biceps tendon to the labrum. We have labeled this injury a "SLAP lesion" (Superior Labrum Anterior and Posterior). There were 23 males and four females with an average age of 37.5 years. Time from injury to surgery averaged 29.3 months. The most common mechanism of injury was a compression force to the shoulder, usually as the result of a fall onto an outstretched arm, with the shoulder positioned in abduction and slight forward flexion at the time of the impact. The most common clinical complaints were pain, greater with overhead activity, and a painful "catching" or "popping" in the shoulder. No imaging test accurately defined the superior labral pathology preoperatively. We divided the superior labrum pathology into four distinct types. Treatment was performed arthroscopically based on the type of SLAP lesion noted at the time of surgery. The SLAP lesion, which has not been previously described, can be diagnosed only arthroscopically and may be treated successfully by arthroscopic techniques alone in many patients.