The expression of 9 tumor-associated antigens (MG7-, MGd1-, MC3-corresponding antigens and CEA, P21ras, sialoglycoprotein, CA19-9-like, sialo-Tn and Lea-like antigens) were investigated on biopsy specimens with different types of intestinal metaplasia (types I, II and III) taken from 112 patients with benign gastric conditions. The incidences of positive staining for all antigens but P21ras in type III intestinal metaplasia were significantly higher than those in types I and II (P less than 0.05-0.001). These 112 patients with intestinal metaplasia were clinico-endoscopic followed-up for 15-70 months. Five of them were found to develop gastric carcinoma within 25-60 months with a cancer detection rate of 4.5%. All the five malignancies were detected in patients with type III (16.1%), none was found in those with types I and II, these differences were significant (P less than 0.05-0.01). Our results indicate that type III intestinal metaplasia has a higher potentiality to evolve to malignancy and that MG7, MGd1, MC3, CEA, CA19-9-like and sialo-Tn antigens are valuable tumor markers in defining the high-risk group of gastric cancer.