Pattern-reversal electroretinograms (PERG) were recorded from 67 subjects, age 55-77 years, with normotensive (n = 19), hypertensive (n = 37) or glaucomatous (n = 11) eyes. The pathological intraocular pressure (IOP) ranged from 23 to 29 mm Hg in 21 eyes and from 30 to 43 mm Hg in 16 eyes. In 11 eyes (11 patients) manifest glaucoma was present (excavated optic disk, visual field defect). All examined subjects had normal visual acuity and clear optic media. The amplitude of the positive component of the PERG was measured. The mean PERG amplitude was 2.8 +/- 1.2 microV in the eyes with normal IOP (19 +/- 3 mm Hg), 2.2 +/- 1.0 microV in the eyes with moderately elevated IOP (26 +/- 2 mm Hg), 2.0 +/- 0.9 microV in the eyes with IOP above 30 mm Hg (33 +/- 4 mm Hg) and 1.1 +/- 0.6 microV in the glaucomatous eyes. Regression lines of PERG amplitudes versus age were calculated in all groups and showed a decrease in amplitude with increasing age. However, the correlation coefficients were not statistically significant. The decline with age was similar in all groups. The results indicate that the PERG amplitude is reduced in glaucomatous eyes and may be reduced also in ocular hypertension as well as with increasing age.