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Traditional methods of serological typing have largely used antisera of Caucasoid origin, which can overlook HLA heterogeneity in non-Caucasoid populations. Therefore, we have used molecular techniques to evaluate potential polymorphism in HLA class I molecules of Aborigines from the central desert and northern coast of Australia. The DNA sequence of common Aboriginal HLA-A and B antigens were compared with serological reaction patterns which suggested new polymorphisms. Although serological data indicated that long and short variants of A34 may exist, regardless of the serological pattern, all individuals carried the A*3401 allele. Therefore, the variation in A34 reaction pattern observed serologically was not attributable to primary sequence variation in the HLA A*3401 allele. Similarly, there was no detectable poly-morhism in the sequences of selected HLA-B alleles, even though some of these alleles showed unusual serological reaction patterns. However, a new allele of B15 (B*1521) was detected in two individuals carrying this serotype. The cells from both of these individuals showed ambiguous reaction patterns with monospecific B62 and B75 sera. cDNA sequencing of the HLA B15 gene from these cells revealed a B15 allele that differed from. B*1502 by a single nucleotide change. This change occurred at position 272, resulting in a C to G substitution at residue 67 in the consensus B15 cDNA sequence. Hence, the Australian Aborigines as an ethnic group show very little primary sequence polymorphism within the class I loci, consistent with the results obtained from previous serological studies.