Twenty-three novel HLA-C alleles are described. Nine of the new alleles are single-nucleotide substitutions from their most homologous allele of which seven result in amino acid changes (Cw*0327, *0508, *0514, *0613, *0735, *0739 and *1517) and two are silent substitutions (Cw*030305 and *070107). The remaining 14 alleles (Cw*0113, *0207, *0212, *0216, *0318, *0411, *0417, *0512, *0722, *0733N, *1216, *1218, *1515 and *1607) differ from their most similar alleles by 2-4 nucleotide substitutions that result in 1-3 amino acid differences.