A prospective gastroscopic-bioptic study of 533 patients was performed to assess the prevalence and distribution of intestinal metaplasia (IM) and its subtypes in the antral mucosa of patients with various upper intestinal disorders and to assess whether the presence of certain IM subtypes might be of help in selecting patients for careful endoscopic-bioptic surveillance in the screening for gastric carcinoma. IM was found in 135 patients (25.3%). Its prevalence increased with age (P < 0.001) and was strongly associated with intestinal-type carcinoma as compared to diffuse-type carcinoma (P < 0.001), gastritis (P < 0.001), and gastric ulcer (P < 0.05). Type I IM was predominant (98.5%), whereas types II and III IM, respectively, were found in 77.8% and 15.6% of the patients with IM. No difference in the prevalence of type I and II IM was found among the various gastric disease states. Type III IM was strongly associated with intestinal-type carcinoma as compared to either benign lesions (P < 0.01) or diffuse-type carcinoma. These results suggest that type III IM may play a special role in the histogenesis of intestinal-type carcinoma and suggest that the finding of this IM subtype in gastric biopsies may possibly be of help in identifying patients at greater risk of developing carcinoma.