The oscillatory potentials of the electroretinogram and other visual function tests were evaluated in a group of 174 diabetic and 54 control subjects. Retinopathy severity in diabetic patients was measured in color fundus photographs and fluorescein angiograms. The summed amplitudes of the oscillatory potentials were significantly lower in diabetic compared with control subjects, and the amplitudes decreased progressively as the retinopathy severity increased. Among diabetic patients, a significant correlation was found between the oscillatory potentials and the other visual function tests; lower amplitudes were associated with lower visual field and visual acuity scores and higher Farnsworth-Munsell 100-hue error scores. Stepwise regression analysis showed that the most important predictors of oscillatory potential amplitudes were retinopathy level, fluorescein leakage, and age; capillary nonperfusion did not add to the predictive power of the model when fluorescein leakage was included.