The neuroretinal rim area of the optic nerve head was measured in 33 normal individuals, 50 subjects suspected of having glaucoma, and 51 patients with glaucoma. The measurements were corrected for magnification produced by the optical system of the eye. The rim areas were statistically highly significantly different in these clinical groups. Mean neuroretinal rim area in the normal controls was 1.40 +/- 0.186 mm2. Therefore, 95% of the normal subjects had rim areas greater than 1.09 mm2; 30% of the subjects with ocular hypertension and 73% of the patients with glaucoma had rim areas less than 1.09 mm2.