A total of 217 cases of gastric intestinal metaplasia (IM), out of 491 cases of consecutive multiple gastric biopsies, were examined using various histochemical methods. Three classifications were adopted (1) Jass and Filipe's (1979), (2) Segura and Montero's (1983), and (3) our own distinguishing two types of small intestine IM (incomplete and complete) and two types of colonic IM (incomplete and complete). Our classification revealed (1) a group of 'pure' IM cases (44%), (2) a group of 'combined' IM cases (15%), either small intestinal or colonic, expressing a maturating line, and (3) a conspicuous group of mixed 'mosaic' IM cases (41%) consisting of all possible combinations between the basic IM types. No significant correlations were found between each IM type and associated diseases (i.e. gastritis, stump gastritis, ulcer, adenoma and adenocarcinoma). However, a suggestive association between colonic IM and malignancy was observed. Our results confirmed the heterogeneity of IM and indicated two differentiation cell lines (ileal and colonic), thus providing additional evidence of impaired maturation and aberrant differentiation along various cell lines, supporting Leblond's (1976) unifying theory on the origin of intestinal epithelial cells.