Gastric adenomatous polyps are rare findings in upper gastrointestinal endoscopy; however, they are associated strongly with malignant transformation. Few series describe the oncogenic characteristics of gastric adenomas. In the present study, we immunohisto-chemically assessed the expression of cyclooxygenase (COX)-2, beta-catenin, p53, and adenomatous polyposis coli (APC) in paraffin-embedded specimens of 14 gastric adenomas. Control samples of normal gastric tissue and gastric adenocarcinoma also were analyzed. Of the adenomas, 7 demonstrated overexpression of COX-2, and all demonstrated nuclear p53 accumulation. Accumulation of beta-catenin in the nucleus and cytoplasm was detected in 38% (3/8) of specimens. Loss of APC staining was observed in 50% (4/8). Similar alterations in oncoprotein expression were seen in gastric cancers but not in normal control sections. Gastric adenomas display alterations in the expression of COX-2, beta-catenin, and APC similar to those seen in adenocarcinomas; however, accumulation of p53 was significantly more common in adenomas than in cancers.