Alterations of the Smad4 gene, identified as a mediator of the transforming growth factor-beta pathway, were investigated in hamster pancreatic duct adenocarcinomas (PDAs) and established cell lines. Female Syrian golden hamsters received 70 mg/kg of N-nitrosobis(2-oxopropyl)amine (BOP) followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine then L-methionine and a further administration of 20 mg/kg BOP. A total of 12 PDAs obtained 10 weeks after beginning the experiment and three cell lines established from subcutaneously transplantable PDAs in syngeneic hamsters were examined for mutations using reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis. A mutation was detected in only one PDA (1/12, 8.3%) in the form of an ACC to ATC (Thr to IIe) transition at codon 73; none were detected in the three cell lines. No reduced or increased expression of the Smad4 gene was detected in any case using real-time quantitative RT-PCR. These results suggest that the Smad4 gene might play a role in limited fraction of BOP-induced pancreatic duct carcinogenesis in hamsters.