Electroretinograms (ERGs) were measured in 65 patients with diabetes and 10 control subjects. The single flash ERGs were recorded as a function of the stimulus intensity. A Naka-Rushton-type function was fit to b-wave amplitudes, measured as a function of stimulus intensity, to evaluate changes in ERG amplitude and sensitivity. We also measured the temporal aspects of the ERG b-waves. The ERG sensitivity tended to decrease as the retinopathy progressed. An average sensitivity loss in eyes with diabetic retinopathy was statistically significant. However, the eyes of diabetic patients without visible retinopathy did not show significant ERG sensitivity loss. There was less variability in temporal compared with amplitude measurements of ERG components, and significantly prolonged b-wave implicit times were found in all stages of retinopathy and in eyes of diabetic patients without retinopathy.