We recorded the pattern electroretinogram (PERG) to small (0.8 degree) and very large (15 degrees) check sizes in normal subjects, in patients with early-stage glaucoma, and in patients with ocular hypertension. In glaucoma, the PERG amplitude was reduced. This reduction was more prominent for a check size of 0.8 degree as compared with 15 degrees stimuli and for high (16/s) as compared with low (7.8/s) reversal rates. Using a discriminant analysis of the amplitudes for two different check sizes, we could distinguish the normal and the glaucoma groups with a specificity of 96% and a sensitivity of 91%. Of the ocular hypertension patients, 43% were classified as pathologic by the discriminant analysis. Thus multivariate analysis of the PERG may increase its diagnostic value.