BACKGROUND/AIMS: Mucins are high-molecular-weight glycoproteins. Aberrant and incomplete glycosylations of mucins have been associated with various human diseases. This study was performed to find the association between mucin protein expression and pancreatic tumors. METHODS: Surgically resected, or radiologically obtained 20 specimens were stained using avidin-biotin-peroxidase methods. The patterns of mucin protein expression were compared between benign and malignant pancreatic tumors. RESULTS: In the neoplastic cells from adenocarcinoma, high levels of MUC1 expression were observed mainly in the cytoplasm, but the expression of MUC2 protein antigens was low compared to MUC1 expression. In benign tumors, there were no differences in terms of staining site and intensity between two mucin protein antigens. The survival rate of the weakly staining group by anti-MUC1 Ab was higher than that of the strongly staining group. The expression of MUC1 protein antigens showed a striking contrast between benign and malignant pancreatic tumors. CONCLUSIONS: Antigens of MUC1 and MUC2 protein seem to be expressed differentially in benign and malignant pancreatic tumors, which may be useful in the diagnosis of malignant pancreatic tumors, especially in ambiguous states.