The CDKN2 (MTS1/p16INK4A) gene, encoding cyclin dependent kinase inhibitor, was found to be homozygously deleted at a high frequency in cell lines from many different types of cancer and some primary cancers. To determine the frequency of CDKN2 mutations in most common human cancers in Korea, PCR and PCR-SSCP analyses for the exon 2 of CDKN2 were performed on each set of 20 formalin-fixed and paraffin-embedded tumor tissues of stomach adenocarcinomas, lung cancers, cervix cancers and hepatocellular carcinomas. No mutations in exon 2 of CDKN2 were found in 20 stomach adenocarcinomas. In contrast to rare mutations in stomach adenocarcinomas, a high frequency of CDKN2 mutations was identified in other 3 cancers, 11 of 20 (55%) lung cancers (7 of 10 NSCLCs and 4 of 10 SCLCs), 14 of 20 (70%) cervix cancers and 11 of 20 (55%) hepatocellular carcinomas. These results suggest that mutations of the CDKN2 gene might be an important genetic change in NSCLCs, cervix cancers and hepatocellular carcinomas.