Unit recordings were performed in the sensorimotor cortex of awake monkeys during performance of learned movements of the contralateral arm. The movements were triggered by a sound stimulus. The neuronal discharge in association with movement was observed before and after deafferentation (C2--T5) of the operant limb. Whereas neurons recorded in the motor cortex (area 4) and in the parietal association cortex (area 5) still modified their activity in relation to movement performed by the deafferented arm, the neurons recorded in the primary sensory cortex (areas3, 1 and 2) showed no activity change in relation to movement after deafferentation. This finding strongly suggests that modification of discharge of postcentral neurons seen during ballistic arm movement is mainly the result of input from the moving limb (peripheral feedback) and not the result of input from other structures of the central nervous system (internal feedback).