The distribution of transferrin alleles in a group of common baboons, Papio cynocephalus of East Africa, was determined after starch gel electrophoresis of plasma and autoradiography of electrophoretograms. Three alleles, TfA, TfB, and TfC, were found, in agreement with results previously reported. The frequencies of these alleles are TfA = 0.276, TfB = 0.515, Tfc = 0.209. The difference between the frequencies reported here and those reported by Buettner-Janusch (1963 Folia Primat., 1: 73–87) for the same species (TfA = 0.205, TfB = 0.332, Tfc = 0.463) is significant. Transferrin of P. cynocephalus contains four residues of sialic acid per molecule of transferrin, as determined by electrophoresis and autoradiography of plasma treated with neuraminidase.