The novel allele HLA-B*1545, which has been serologically typed as B62, was identified in a male Caucasian. In the sequence analysis the new allele differs from B*1507 by nucleotide 419 which is located in exon 3. Its structure suggests that it may have originated by a point mutation or by gene conversion with a variety of HLA-B alleles. At the protein level, the nucleotide substitution results in an amino add exchange compared to B*1507 (Tyr116Ser). Due to probably substantial differences to B*1507 and the other B*15 variants with regard to peptide binding, a mismatch is likely to impair clinical outcome of bone marrow transplantation.