Background The anion exchanger, Band 3, carries antigens in the Diego blood group system, and can carry the Band 3-Memphis phenotype. Although Dib is of high prevalence and Band 3-Memphis is of low prevalence in humans, it has been suggested that both are on the ancestral gene. We determined the orthologue nucleotide sequences corresponding to these two polymorphic sites, Dia/Dib (2561T > C; Leu854Pro) and Band 3-Memphis(166A > G; Lys56Glu) in several nonhuman primates. Methods Genomic DNA was extracted from blood samples of great apes, lesser apes, old world monkeys, new world monkeys and prosimians. PCR amplifications were done with primer pairs that were located in the flanking intronic regions of Exon 4 and Exon 19; and the amplified products were sequenced. Results Amino acid sequence alignment of nonhuman primates band 3 with that of human showed extensive homologies. In exon 4, Glu56Lys polymorphic site showed Glu similar to Band 3-Memphis type and in exon 19, Leu854Pro polymorphic site showed Pro indicating Dib phenotype. Conclusions The nonhuman primates have nucleotide sequences of Dib(2561C) in cis to Band 3-Memphis (166G), which is consistent with the assertion that the Dib and Band 3-Memphis phenotype represents the ancestral Band 3 gene. [ABSTRACT FROM AUTHOR]