The presence of an unusual HLA class I reactivity pattern was detected in a Caucasoid-Asian individual by PCR-sequence specific primer (PCR-SSP) typing. Exons 2 and 3 were characterized using PCR-sequence-based typing (PCR-SBT) and were found to contain a novel Cw*03 sequence, Cw*0315. In the region studied, Cw*0315 was comprised mainly of the Cw*0302 sequence, but at four positions it contained nucleotides normally only found in other HLA Cw locus alleles. These positions each resulted in an amino acid substitution.