Background/Aims: The transition from intestinal metaplasia to adenocarcinoma is characterized by further qualitative and quantitative alterations of mucin-related carbohydrate antigens. The aims of this study were to examine expression patterns of mucin-related carbohydrate antigens, to investigate the relationship between the expression patterns and prognostic factors, and to evaluate the usefulness of the expression patterns in assessing the progression of gastric carcinoma. Methods: Immunohistochemical studies of 3 carbohydrate antigens (Tn, sTn, sLex) were performed for 63 gastric carcinoma tissues (EGC:23 cases, AGC:40 cases) and 54 gastric epithelial dysplasia tissues obtained from January 1997 to December 1997. Results: The carbohydrate antigens were significantly expressed in advanced gastric cancer. By the results of immunohistochemistry for Tn and sTn antigens, distribution and intensity of staining were also significantly increased in progression to advanced gastric cancer. Especially, dysplastic lesions had the tendency to show supranuclear Golgi staining pattern, and carcinomas showed diffuse cytoplasmic pattern or luminal border pattern of neoplastic glands. The expression of Tn antigen was significantly increased in carcinomas with deep invasion. The expressions of Tn and sLex antigens were significantly increased in advanced gastric cancer with lymph node metastasis. Conclusions: These results suggest that the expression patterns of the mucin-related carbohydrate antigens may be correlated with prognostic factors and predict the progression from gastric epithelial dysplasia to advanced gastric cancer. (Kor J Gastroenterol 2000;35:732 - 745)