Major League Baseball (MLB) players are at significant risk for both chronic, repetitive overuse injuries as well as acute traumatic injuries. Pitchers have been shown to be at higher risk for sustaining injuries, especially upper extremity injuries, than position players. The past several MLB seasons have seen a dramatic rise in the number of ulnar collateral ligament reconstructions performed in MLB pitchers. Several recent prospective studies have identified risk factors for injuries to both the shoulder and elbow in MLB pitchers. These risk factors include a lack of external rotation, a lack of total rotation, and a lack of flexion in the throwing arm. Thus far, no study has demonstrated a correlation between cumulative work (number of games pitched, total pitches thrown, total innings pitched, innings pitched per game, and pitches thrown per game) and injuries in MLB pitchers, despite several studies showing this correlation in youth pitchers. Although many risk factors have been translated into guidelines for prevention, no study has been conducted to determine whether adherence to these guidelines effectively prevents injuries. Further studies are necessary to define exactly how injuries in MLB players can be prevented.