One hundred and ten novel MHC-DRB gene exon 2 nucleotide sequences were sequenced in 96 monkeys from three owl monkey species (67 from Aotus nancymaae, 30 from Aotus nigriceps and 13 from Aotus vociferans). Owl monkeys, like humans, have high MHC-DRB allele polymorphism, revealing a striking similarity with several human allele lineages in the peptide binding region and presenting major convergence with DRB lineages from several Catarrhini (humans, apes and Old World monkeys) rather than with others New World monkeys (Platyrrhini). The parallelism between human and Aotus MHC-DRB reveals additional similarities regarding variability pattern, selection pressure and physicochemical constraints in amino acid replacements. These observations concerning previous findings of similarity between the Aotus immune system molecules and their human counterparts affirm this specie's usefulness as an excellent animal model in biomedical research.