Nontraumatic shoulder pain in the adult overhead athlete is a common problem. The exact biomechanical adaptations that predispose the overhead athlete to injury can be multifactorial in nature, including range of motion deficits, muscular imbalances, and scapular dyskinesis. It is imperative that the rehabilitation professional not only correctly identify and treat the direct cause of the pain, but also initiate a rehabilitation program aimed at improvement of the underlying biomechanical deficits that predispose the overhead athlete to shoulder injury. This only can be accomplished through a better understanding of the most common biomechanical deficits that the overhead athlete develops and how to treat them. This article focuses primarily upon shoulder training in the adult baseball pitcher as a classic example of an overhead athlete.