The effects of conditioning facial (trigeminal and facial nerves, second cervical roots), peripheral (radial and sural nerves), auditory and visual stimuli on the blink reflex components have been studied in normal subjects. In all the RI response was facilitated and the R2 one was inhibited. By electrophysiological techniques it has been shown that this inhibition is due to a synaptic phenomenon and that the conditioning afferents converge on the same neuronal pool. An unspecific mechanism is proposed to account for these data.