Background: The curveball has been anecdotally considered as a dangerous pitch among youth pitchers, especially for their ulnar collateral ligaments. No biomechanical studies have been conducted among youth pitchers comparing different types of pitches. Hypothesis: The kinetics of the baseball throw varies significantly between the fastball, curveball, and change-up for youth pitchers. Kinematic and temporal differences are also expected. Study Design: Controlled laboratory study. Methods: Twenty-nine youth baseball pitchers (age, 12.5 ± 1.7 years) pitched 5 fastballs, 5 curveballs, and 5 change-ups with maximum effort in an indoor laboratory setting. Data were collected with a 3-dimensional motion analysis system. Kinetic, kinematic, and temporal parameters were compared among the 3 pitches. Results: For elbow varus torque, shoulder internal rotation torque, elbow proximal force, and shoulder proximal force, the fastball produced the greatest values, followed by the curveball and then the change-up. The fastball also produced the greatest elbow flexion torque. Shoulder horizontal adduction torque and shoulder adduction torque were the least for the change-up. Several differences in body segment position, velocity, and timing were also found. Conclusions: In general, elbow and shoulder loads were the greatest in the fastball and least in the change-up. Kinematic and temporal differences were also found among the 3 pitch types. Clinical Relevance: The curveball may not be more potentially harmful than the fastball for youth pitchers. This finding is consistent with recent epidemiologic research indicating that amount of pitching is a stronger risk factor than type of pitches thrown. © 2008 American Orthopaedic Society for Sports Medicine.