We measured vertical and horizontal diameters of the optic disk and retrobulbar optic nerve in eyes from 95 patients on whom autopsies were performed at the UCLA Medical Center over a 20-year period. Ages at death ranged from 4.8 months' gestation to 21.9 years. Optic disk surface area and nerve cross-sectional area were calculated for each subject by using the formula for an ellipse. Approximately 50% of the growth of the optic disk and nerve occurs by 20 weeks' gestation, and 75% by birth; 95% of the growth occurs before the age of 1 year. All optic disk and nerve measurements correlate strongly (correlations > .67; P < .0001) with subject height and globe anteroposterior diameter. We applied our results to the current understanding of optic disk and nerve development, and compared them to previous clinical and pathologic studies of optic nerve dimensions in adults and older children.