To investigate how GABAA inhibition in the motor cortex is involved in motor control in freely moving infant macaque monkeys, muscimol, a GABAA agonist, was injected into the hand motor area and changes in movement parameters of visual reaching during apple pickup tests or a delayed response task were examined. After the injection (30 micrograms microliters-1) the monkeys tended to use the contralateral hand, and the ipsilateral hand showed a posture of dropped wrist and fingers, as if the radial nerve were paralysed. Movement time and/or reaction time of the ipsilateral hand was prolonged. Motorcortical GABAA inhibition is important for initiation of smooth flexion and/or extension movement of the hand and fingers.