The neuroretinal rim as equivalent of the retinal nerve fibers is the target in the evaluation of glaucomatous optic nerve heads. Its area was measured in absolute size units using photographs of 234 normal optic disks and correcting the photographic magnification according to Littmann's method. High myopic eyes (less than -8.00 dptr) were excluded. The mean rim area was 2.09 +/- 0.60 (0.80-3.80 mm2). It was significantly correlated (p less than 0.00001) to the optic disk area. In optic disks without cupping, the neuroretinal rim area was identical with the disk area (r = 1.0, slope of the regression line = 1.0). In disks having cups with temporal flat slopes, the rim area increased by a factor of 0.71 with the disk size, in disks with circular steep cups, by a factor of 0.26. This interindividual variability and the correlations between rim and disk area might be clinically important for morphometry of glaucomatous optic nerve heads. There were no significant correlations between rim area and age, sex, refraction or axial length.