A topographic map of nerve fiber layer thickness was prepared from serial sections of the retina of the cynomolgus monkey. Montage electron micrographs of the nerve fiber layer were used to determine the relative proportions of axons and of glial processes within a given nerve fiber bundle at various positions across the retina. The cross-sectional area of nerve fiber bundles occupied by glia was never less than 18%, and in most cases was 20-30%. The proportion of glia in the bundles varied from point to point across the retina without respect to nerve fiber layer thickness and at some locations was as much as 42%.