HLA-C alleles have always been the least well characterized of the HLA class I genes. At present, 36 HLA-C alleles have obtained an official designation. The eight specificities Cw1 to Cw8 comprise a total of 19 alleles. In addition 17 alleles have no serological counterpart, they are typed as `blanks`. Since only detailed analysis of HLA-C alleles will help to assess the influence of HLA-C on the allogenic immune response, It seems essential to characterise HLA-C alleles at the nucleotide level. In order to identify serologically detectable and undetectable HLA-Cw antigens, we used a sequence-specific primer (PCR-SSP) system using twenty three PCR mixtures for assigning HLA-C alleles. This typing approach has been validated on 12 control cells and serologically typed unrelated Korean individuals. The results of 12 control cells correlated well with the data which were previously reported. The serologically undefined `blank` antigens were succesfully typed by DNA typing. The PCR-SSP method for HLA-C is a rapid technique, sensitive and reproducible and capable of distinguishing serologically undetectable HLA-C alleles.