Dark adapted and progressively light adapted electroretinograms (ERGs) were recorded from 34 normals and from 45 glaucoma patients. To enhance the oscillatory potentials (OP) the ERGs were highpass-filtered. The OP were characterized by two indices: their root-mean-square value and the inter-flash interval for which the maximal amplitude was obtained. In most of the glaucomatous OP, 50 of 81 eyes, both indices were abnormal, in 22 one parameter was abnormal and only in 9 were both parameters normal. In 13 of the 14 OP recorded from the opposite ('normal') eye of patients with unilateral glaucoma either one or both of the indices were abnormal. These findings indicate that the damage to the retina in glaucoma may extend more distally than the ganglion cell layer and that subclinical changes might be revealed by OP changes.