We attempted to establish a computed tomographic value representing the normal volume ratio of gray matter to white matter (G/W) in children in order to have a baseline for studying various developmental disorders such as white matter hypoplasia. The records of 150 children 16 years of age or younger who had normal cranial computed tomography were reviewed. From these a group of 119 were excluded for various reasons. The remaining 31 were presumed to have normal brains. Using the region of interest function for tracing gray and white matter boundaries, superior and ventral to the foramen of Munro area, measurements were determined for consecutive adjacent frontal slices. Volumes were then calculated for both gray and white matter. A volume ratio of 2.010 (sigma = 0.349), G/W, was then derived from each of 31 children. The clinical value of this ratio will be determined by future investigation.