Three alleles encoding molecules with the B56 serologic specificity have been reported thus far. This study characterized an additional allele encoding a B56 molecule from two unrelated Korean individuals. The novel allele, B*5604, differs from B*5602 by a single nucleotide substitution at codon 103 (CTG-->GTG) resulting in an amino acid change from leucine to valine. The putative haplotype associated with the novel allele was A2-B*5604-Bw6-Cw7-DRB1*15-DRB5*02-DQA1*01-DQB 1*05.