The radius of curvature of the posterior surface of the cornea was measured in the vertical meridian for 120 children aged 6 to 17 years, using a Purkinje image method. The mean radius of curvature (+/-SD) was 6.42 +/- 0.31 mm, with a range from 5.62 to 7.22 mm. The ratio of anterior to posterior corneal radius was 1.210 +/- 0.045 or 0.827 +/- 0.029 when expressed as a reciprocal. There was a significant correlation between the anterior and posterior corneal radius (y = 0.798x + 0.228, r2 = 0.45). The study provides data that may be applied to a four-surface schematic eye.