The evolutionary relationships among Mhc-DPA1 alleles of various nonhuman primate species was studied by sequence analysis of exon 2. Here we report the nucleotide sequences of 15 Mhc-DPA1 alleles obtained from several great ape and Old and New World monkey species. Comparison with their human homologues reveals that alleles can be grouped into transspecies lineages, indicating that some HLA-DPA1-associated polymorphisms have been maintained for at least 35 million years.