HLA-B67 is an uncommon antigen that has been defined by serological crossreactivity with the HLA-B7 and HLA-B16 (B38 and B39) antigens. It is found at highest frequency in certain Oriental populations and has been best defined in the Japanese. Nucleotide sequencing of cDNA encoding B67 reveals the B*6701 allele to be a subtype of B39 which differs from B*39011 by substitution at residues 67-71 of the alpha 1 helix. In the region of difference B*6701 is identical in sequence to B7, B22, B27 and related molecules that express the epitope recognized by the ME1 monoclonal antibody. That the HLA-B67 molecule binds strongly to the ME1 antibody was demonstrated by immunoprecipitation and cell surface binding assays. Identical B*6701 nucleotide sequences were obtained for the B67 alleles isolated from 2 unrelated Japanese and 1 North American caucasoid.