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This study aimed to demonstrate each joint angle at the maximum external rotation of the shoulder complex during the throwing of adolescent baseball players. The subjects were 15 adolescent baseball players (13.7±0.8 yrs) and 15 collegiate baseball players (22.1±1.5yrs). Throwing motion images were captured by three high-speed cameras, and a 3D analysis established by the direct leaner translation method was performed to obtain the shoulder external rotation, the glenohumeral external rotation (ER), and scapular posterior tilt angles. In the adolescent baseball players, the mean (±SD) value of the maximum external rotation angle (MER) was 141 ±15°, whereas the mean values of the glenohumeral ER and the scapula posterior tilt angles at the MER were 109±15° and 31±14°. Conversely, each angle of the college baseball players was 144±11°, 107±15°, and 29±14° respectively. There were no differences between the adolescent players and the college players. The adolescent players may need the same shoulder joint angles as the college players [ABSTRACT FROM AUTHOR]