Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and the 5T genotype of the polythymidine tract at the exon 9 splice branch/acceptor site are shown to be associated with chronic pancreatitis in Caucasian patients. In contrast to Western countries, cystic fibrosis is extremely rare in Japan. In this study, we investigated the association of mutations or polymorphisms of the CFTR gene with chronic pancreatitis in Japanese patients. Forty-seven patients with chronic pancreatitis (alcohol-related in 31, idiopathic in 14, and familial in 2) were examined for the deltaF508 and R117H mutations and polymorphisms of intron 8. DNA was extracted from leukocytes. Mutations and polymorphisms were examined by the allele-specific polymerase chain reactions and confirmed by direct sequencing. None of the patients had deltaF508 or R117H mutations in the CFTR gene. All of 47 healthy Japanese showed the homozygous 7T/7T genotype, whereas the frequencies of 5T, 7T, and 9T alleles were 0.043, 0.894, and 0.064 in the patients, respectively. The difference in allele frequency is statistically significant. Therefore, the present study indicates the association of polymorphism of the polythymidine tract in intron 8 of the CFTR gene with chronic pancreatitis in Japanese patients.