Of all HLA class I molecules, HLA-C gene products are most poorly understood because they express at a low level on the cell surface compared to HLA-A and -B. In order to identify serologically detectable and undetectable HLA-C antigens, we have established a DNA-based tissue typing method for the HLA-C locus by PCR-SSP (polymerase chain reaction-sequence specific primers). Genomic DNA prepared from Iymphoblastoid 21 B-cell lines and 120 Korean individuals by proteinase K digestion and pheno/chloroform extractions have been typed by PCR-SSP (23 primer mixes were used). The PCR-SSP results of control cell lines were discrepant from serology in 1 case among 21 cases: Cw6 which was negative by serology but positive by PCR-SSP (cell line: MANIKA). Twenty four HLA-Cw "blank" antigens among fifty Korean individuals were completely determined by PCR-SSP DNA typing. HLA-Cw*0101 (15.3%), Cw*1401 (12.3%) and Cw*0701 (11.7%) alleles were frequently found in 120 Korean individual samples. In conclusion. the high level of discrimination for HLA-C alleles may prove useful and informative in the study of transplant survival, and identify the importance of allelic differences, not readily detectable by serology, on host and donor compatibility.