We conducted this study to determine whether a test, the posterior impingement maneuver, could be used to prospectively identify articular side tears of the rotator cuff and/or posterior labrum. Sixty-nine athletes presented with posterior shoulder pain that developed during overhand athletics. Injured shoulders were placed into 90 degrees to 110 degrees of abduction, slight extension, and maximum external rotation, and an effort was made to elicit pain deep within the posterior aspect. Overall sensitivity of the test was 75.5%, and specificity was 85%. When only athletes with noncontact injuries (gradual onset of pain) were considered, sensitivity was 95% and specificity was 100%. A positive posterior impingement sign correlated highly with undersurface tearing of the rotator cuff and/or tearing of the posterior labrum in athletes with gradual onset of posterior shoulder pain during overhand athletics.