Necropsy data from a Primate Center were used in a study of the brain weight-body weight relationships of 12 species of nonhuman primates. The sample sizes ranged from six Cercopithecus aethiops to 163 Macaca mulatta. By plotting mean brain-mean body weight of each species on log-log paper, it was shown that the straight line fitting the plots of all species had a slope of 0.72. Slopes for three species of the genus Macaca, and for six species of the family Cebidae, were 0.61 and 0.81 respectively. Coefficients of determination of the three lines were greater than 0.90. Two species of the family Cebiade, Saimiri sciureus and Aotus trivirgatus, had equivalent body weights, but the former had a 30% larger brain than the latter. The results suggest that brain-body weight scaling characteristics of primate species can be studied effectively using necropsy data. Some statistically significant discrepancies between these and published data, however, show that more data are required to describe these characteristics with greater certainty.