In 15 healthy subjects we studied body sway reactions to sinusoidal 0.3 Hz binaural bipolar galvanic current up to 2 mA under three conditions. With the head forward and eyes closed, there is only a periodic lateral displacement of the centre of gravity, following the stimulation with a phase lag. In two other conditions, the head turned to the left or to the right without trunk torsion, the direction of sway was modified in such a way that there were mainly anteroposterior movements. It is thought that this experiment shows the modulatory influence of neck afferents on the direction of vestibulospinal motor effects in man.