Various genetic changes are involved in progression of various cancers. We examined alterations (deletion, sequence abnormalities, methylation) of the CDKN2A gene in cell lines and tumor tissues of pancreatic cancers. Some alterations of this gene were found in all the 12 cell lines examined. In the primary lesions of pancreatic cancers, homozygous or hemizygous deletion were found in 8 of 24 ductal carcinoma and 4 of 9 other types of carcinomas. It appears that there is an association between the alteration of this gene and tumor size, regional lymph node metastasis and hematogenous distant metastasis in the ductal carcinoma, but not in the other types of carcinomas. All the 5 liver metastatic lesions of the ductal carcinoma examined revealed homozygous or hemizygous deletion and 3 bp deletion. These results suggest that inactivation of the CDKN2A gene occurs more frequently in cell lines than in pancreatic cancer tissues. Such genetic events on the CDKN2A gene may play an important role possibly at a later step in the progression of pancreatic ductal carcinoma.