WE have examined the haptoglobin types of a series of blood samples from 27 monkeys (23 Macaca mulatta, 1 Macaca irus and 3 Cebus nigrivittatus). The Macaca mulatta and Macaca irus, indigenous to India and Java, were purchased from the United States (Trefflich's Bird and Animal Co. Inc.). Since the rhesus monkey species infrequently reproduces itself in captivity, it can be assumed, even though no genetical results were obtained, that these monkeys are probably unrelated. The few Cebus samples examined came from the Higuerote (Miranda State) and Tamanaco (Guarico State) regions, in Venezuela.