The competitive athlete who participates in a sport requiring overhead motion depends on a shoulder with optimal function. An acute episode of injury or a gradual onset of symptoms in the shoulder can affect the athlete's ability to perform. An understanding of shoulder anatomy and function is essential, and an accurate diagnosis of the underlying pathology is critical for planning treatment options. The correct diagnosis may be less clear when the athlete presents with an insidious onset of shoulder pain. A detailed history and physical examination, as well as an evaluation of the overhead motion and onset of pain, is important when the diagnosis of instability or impingement is considered. Rehabilitation of the rotator cuff often succeeds in alleviating symptoms and restoring function. Surgery is considered when symptoms and diminished function persist despite appropriate nonoperative treatment. Operative repair or reconstruction must be anatomical in nature. Postoperative rehabilitation is equally important in this setting, and a motivated athlete helps to ensure success.