Intestinal metaplasia (IM) have long been thought to play a role in the pathogenesis of gastric intestinal adenocarcinoma, but not in that of diffuse cancer. We studied 20 normal gastric mucosa, 90 IM, 39 atypia (dysplasia or adenoma), and 51 adenocarcinoma to evaluate the expression of p53, erb B2, and H-ras p21 proteins and to assess the correlation with IM (esp. type III IM, revealing positive HID-AB/PAS for sulfomucin). Positive rate of HID-AB staining revealed an increased trend in comparison between IM, atypia and adenocarcinoma. It was the highest in mucinous carcinoma, but it was not correlated with positive oncoprotein expressions. Positive rates of oncoproteins revealed increased trends in comparison between IM, dysplasia or adenoma and adenocarcinoma in c-erb B2 and p53 (P<0.01). The positive rates were highest in intestinal adenocarcinoma (50.0% and 54.2%, respectively). Rates were lowest in biopsy tissue of IM (4.4% and 8.7%, respectively). The expression of H-ras p21 was not significant in gastric carcinogenesis. There was no significant correlation between oncoproteins and other clinical parameters, such as depth of invasion, differentiation, size and nodal metastasis of the tumors. Therefore, we suggest that p53 and erb B2 may play a role in the carcinogenesis of gastric intestinal adenocarcinoma.