BACKGROUND/AIMS: The Bcl-2 protooncogene, located on chromosome 18, codes for a 26 kd protein involved in inhibiting programed cell death (apoptosis). Recent studies have revealed a close relationship between aberrant expression of Bcl-2 and various human malignancies. The aim of this study was to investigate the immunohistochemical expression of Bcl-2 in the gastric adenoma and gastric adenocarcinoma. METHODS: Immunohistochemical staining using monoclonal Bcl-2 antibody, clone 124, was performed on paraffin embeded specimens. The specimens were obtained from 23 gastric adenomas and 23 gastric carcinomas. RESULTS: Seventeen of 23 adenomas (74%) and 3 of 23 adenocarcinomas (13%) were Bcl-2-positive in immunohistochemical staining. The expression rate of Bcl-2 in adenocarcinona was lower than that in adenoma. In gastric adenoma, Bcl-2 expression was not correlated with relevant clinicopathological parameters such as histological grade, location, and size. CONCLUSIONS: The Bcl-2 expression would be found in the early phase of gastric carcinogenesis. It is suggested that the Bcl-2 expression would be related with the development of differentiated gastric adenomas, but not with the development or progression of gastric carcinoma.