Abstract: Disclosed is a motor driven arm rehabilitation device which includes a rotatable forearm support structure capable of being rotated back and forth through a predetermined arc at a predetermined speed and with a predetermined force applied, and a fluid motor such as a rotary actuator for rotating this support structure. Rotation of the supporting structure causes alternate flexion and extension of the patient's arm. The arc of rotation, frequency of rotation and force applied can be varied in accordance with the patient's needs. Associated with the forearm supporting structure is a wrist stabilizer which causes alternate pronation and supination of the wrist as the forearm is alternately flexed and extended. The device also has an upper arm supporting structure.