Oncogenes, tumor suppressor genes, and growth factors are being explored as to their role in the initiation and progression of most neoplasms, but little information exists on the expression of oncoproteins or growth factors in adenocarcinoma of the duodenum or ampulla of Vater. This report covers expressions of p53, c-neu, TGF-alpha, CEA, and EMA in duodenal adenocarcinoma and ampullary adenocarcinoma, as well as correlations between expressions and tumor stage, histological grade and patient survival. The expression of p53, c-neu, TGF-alpha, CEA, and EMA has been studied in 15 duodenal adenocarcinomas and in eight ampullary adenocarcinomas by avidin-biotin-peroxidase complex indirect immunoperoxidase technique. The positive reaction for p53, c-neu, TGF-alpha, CEA, and EMA in duodenal adenocarcinoma was 20%, 60%, 60%, 73%, and 100%, respectively, and in ampullary adenocarcinoma, 13%, 100%, 50%, 63%, and 100%. Among the duodenal tumors, C-neu and p53 expression was noted more frequently in groups with high histological grades. Patients with c-neu positive duodenal adenocarcinoma had a shorter survival than the patients with c-neu negative duodenal adenocarcinoma (P < 0.01). C-neu product may serve as an unfavorable prognostic indicator in duodenal adenocarcinoma. No statistically significant correlation was found between the expressions of CEA, EMA, p53, and TGF-alpha and patient survival, tumor stage, or histological grade in either duodenal or ampullary adenocarcinomas.