Average normal values for the VER were obtained in children aged 4 to 11 years. There are slight but significant differences between the values obtained and those found in adults (an increase in the time to peak of P1). In amblyopic eyes the time to peak is increased, and the amplitude reduced, roughly in proportion to the loss of visual acuity and binocularity. The VER is normal in the better eyes of children who have never been treated by occlusion therapy. Occlusion increases the time to peak of the VER, both in serial studies on individuals, and in lateral population studies, so that the response of the better eye is delayed beyond that of the amblyopic eye. After the end of occlusion, the VER change usually returns to normal. In a subgroup of patients with prolonged occlusion, the changes had not completely reversed one year later. In children in whom occlusion therapy had improved visual acuity, the VER returned towards normal.