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The aim of the study was to clarify the biomechanical differences among the overhand (OS), three-quarter (TS), sidearm (SS) and underhand (US) styles of baseball pitching. About 700 pitches were videotaped using the 3D DLT method. The fastest pitch of each pitcher was used to establish criteria for the separation of the pitches into the four styles based on coaches’ observation and on trunk lateral tilt and upper arm elevation angles. Forty-nine pitches were selected for analysis, and classified into 18 OS, 10 TS, 10 SS and 11 US deliveries. Twenty-six kinematic and kinetic variables were calculated and analyzed. Trunk lateral tilt and upper arm elevation angles were significantly larger in the order OS-TS-SS-US. Ball velocity was significantly slower in the US group than in the other three. Significant differences were found among the groups in six kinematic and five kinetic variables. The slow ball velocity in the US group may have been causally linked to the significantly smaller forces and torques of the US group in relation to the other three.