Optic disc measurements were performed with computerized image analysis (Rodenstock Optic Nerve Head Analyzer) in one eye of each patient of 74 normal controls, 41 ocular hypertensives and 41 patients with early stage glaucoma. In normal controls, the rim area was 1.62 +/- 0.48 mm2 (mean +/- s.d.), cup area 0.80 +/- 0.41mm2, cup volume 0.34 +/- 0.16mm3, cup/disc ratio 0.43 +/- 0.19. For Ocular hypertensives, rim area was 1.32 +/- 0.44mm2, cup area 1.32 +/- 0.78mm2, cup volume 0.56 +/- 0.41mm2, cup/disc ratio 0.51 +/- 0.41. For glaucomas, the rim area was 1.07 +/- 0.47mm2, cup area 1.3 +/- 0.78mm2, cup volume 0.75 +/- 0.40mm3, cup/disc ratio 0.65 +/- 0.19. Statistically significant differences were found among the three groups for these parameters. In spite of the wide distribution and overlap of the values of optic disc parameters among the three groups, normal subjects with an optic disc area of greater than or equal to 3.0mm2 showed clear differences in optic disc parameters compared to ocular hypertensive and glaucoma cases. From these results, cases with larger discs seem to be more vulnerable to raised IOPs.