Expression of the molecular biological factors (MBFs) c-erbB-2, Ki-67 antigen, and tenascin (TN) was assessed immunohistochemically in specimens from patients who had undergone surgery for carcinoma of the papilla of Vater. The MBFs were then analyzed by histological factors (v, d, panc, n, Stage), which have been demonstrated to be outcome predictors, and by patient outcome. None of the MBFs showed any significant correlation with the histological factors. There were significant differences (p < 0.05) in the expression of c-erbB-2, Ki-67 antigen, and TN between patients who survived >5 years and those who survived <5 years. The patients with greater expression of c-erbB-2, Ki-67 antigen, and TN had a poor prognosis, whereas those with less expression had a good prognosis. They were therefore considered independent predictors of outcome for carcinoma of the papilla of Vater. Combined analysis of both histological factors and MBFs was also performed, with the result that the combined analysis of MBFs yielded a better prediction of outcome in carcinoma of the papilla of Vater than analysis of either one histological factor or MBF.