The novel HLA-Cw*0704 allele, previously detected as the PCR-SSP variant Cw7/8v, has been cloned and sequenced from the homozygous typing cell KRO3/4 after amplification by anchored PCR. The nucleotide sequence of Cw*0704 is closely related to those of other Cw*07 alleles, but carries specific changes in exon 3 consistent with its serological behavior-a short Cw7 cross-reactive with antibodies directed against HLA-Cw8. Some of the substitutions of Cw*0704 have not been previously described for HLA-C but are found in HLA-B alleles and in published C sequences of non-human primates. The new allele carries a novel polymorphism in its 5' untranslated region (5' ut) that could be shared by all Cw*07 alleles. By PCR-SSP, Cw*0704 is a relatively common allele in English Caucasoids at a frequency of 4.6%. It is most often observed on HLA-B44 haplotypes previously described as HLA-C "blank", although linkage disequilibria with other HLA-B specificities have been found.