Because of the difficulty in obtaining biopsy specimens from pancreatic cancer patients, K-ras mutation analysis in pancreatic juice has been used for specific diagnosis. But recently, false positives have been obtained with this method. To improve the genetic diagnosis of pancreatic cancer, detection of p53 gene mutation in pancreatic juice was studied. Pancreatic juice was sampled endoscopically. Single-strand conformation polymorphism analysis was used for p53 mutation analysis. Furthermore, K-ras mutations at codon 12 were also studied in the same pancreatic cancer patients. Of 26 cases of pancreatic cancer, p53 mutations were detected in 11 (42.3%). No mutations were seen in the cases with mucin-producing adenoma nor with chronic pancreatitis. K-ras mutations were detected in 84.0% of cases by RFLP analysis, which has high sensitivity, and in 65.3% by hybridization protection assay, which has high specificity. Using a combination assay with both genes, genetic abnormalities were detected in 92.0% by RFLP and 73.1% by hybridization protection assay including two cases in which p53 alone was positive by both methods. The specificity of p53 mutation for pancreatic cancer is very high. Therefore, simultaneous analysis of p53 and K-ras mutation is suggested to enhance the genetic diagnosis of pancreatic cancer.