The patterns of five red cell enzymes (acid phosphatase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, adenylate kinase, and phosphoglucomutase ) in various Anthropoidea were compared on starch gels. Small samples of gorilla, orang, and gibbon, six genera of Old World monkeys, and seven genera of New World monkeys were examined. Among the hominoids the gibbon was the most divergent. The langur differed markedly from macaques and baboons in certain enzyme patterns. Most of the ceboids had relatively high G6PD activities. Individual variations in 6PGD, AP, AK, and PGM but not in G6PD were seen in some species. Many genera could be distinguished by the mobility of the achromatic bands.