The tennis player places unique demands on the shoulder by creating a high risk for overuse and overloading of the soft tissues. Tennis requires concentric work to position and move the arm, eccentric work to stabilize the shoulder, effective depression of the humeral head to avoid impingement in the overhead position, and normal stability to prevent secondary impingement. The tennis serve produces enormous angular velocities about the shoulder joint. A comprehensive rehabilitation program has been described in which the therapist, trainer, player, and physician alike need to have an understanding of the basic biomechanics of this sport. This program can be used to treat the painful shoulder, prevent injury, and enhance performance.