Measurements have been taken of the crowns of the teeth of seventy-nine chimpanzees, eighty-nine gorillas and sixty-three orang-outangs. Basic statistical data, comprising the mean, the number of skulls, the standard deviation and the standard error of the mean, are presented for forty-eight dimensions and indices of the deciduous teeth and for seventy-eight of those of the permanent dentition of each type of ape. A separation between the sexes has been made in the case of the permanent teeth. Further separation has been made into age groups, where necessitated by changes in dimensions due to wear. Even with the small samples resulting from these subdivisions, the standard error is seldom greater than 4% of the mean, and therefore the figures obtained are reliable estimates of the variability of the teeth of apes. The data provide a basis for quantitative comparisons between the teeth of existing and fossil anthropoids.