Nine novel HLA-A and HLA-B alleles are described: A*2609, A*6803, A*6806, B*1539, B*1540, B*2712, B*4103, B*5109, and B*5603. Most appear to have arisen by gene conversion events. B*5603 appears to have arisen by a reciprocal recombination event joining exon 2 of a B*55/ *56 allele with exon 3 of a B*15 allele. Serologically, the antigen encoded by this allele types with broad B22- and Bw6-specific alloantisera. Also unique, the antigen encoded by B*2712 does not react with B27-specific alloantisera but does react with Bw6-specific alloantisera.