The expression of ϵ‐ and γ‐globin mRNA and protein has been determined in three Old World monkey species (Macaca mulatta, Macaca nemestrina, and Cercopithecus aethiops). Using RT‐PCR with primers for ϵ‐ and γ‐globin, both mRNAs were detected in early fetal stages, whereas at 128 days (85% of full term), only γ was expressed. High‐performance liquid chromatography was used for separation and quantitation, and matrix‐assisted laser desorption/ionization mass spectrometry was used for identification of globin polypeptides. An α‐globin polymorphism was observed in all of the species examined. During fetal life, γ‐globin was the predominant expressed β‐type globin. The red blood cells of infants still contained substantial amounts of γ‐globin, which declined to negligible levels in 14 weeks as β‐globin expression reached adult values. The ratio of γ1‐ to γ2‐globins (equivalent to ^Gγ/^Aγ in humans) was approximately 2.5, similar to the ^Gγ/^Aγ ratio observed in humans. Thus, γ‐globin gene expression in these Old World monkeys species has three features in common with human expression: expression of both duplicated γ genes, the relative preponderance of γ1 over γ2 expression, and the delay of the switch from γ‐ to β‐globin until the perinatal period. Thus, the catarrhines seem to share a common pattern of developmental switching in the β‐globin gene cluster, which is distinct from the timing of expression in either prosimians or the New World monkeys. Our results indicate that an Old World monkey, such as Rhesus, could serve as a model organism (resembling humans) for experimentally investigating globin gene expression patterns during the embryonic, fetal, and postnatal stages. J. Exp. Zool. (Mol. Dev. Evol.) 288:318–326, 2000. © 2000 Wiley‐Liss, Inc.