Abstract. Mucin is a high molecular weight glycoprotein that plays an important role to protect the gastrointestinal tract epithelium. However, in cancer cells and during cancer progression, the expression profile of mucins is altered and expression of some mucins is correlated with prognosis for certain malignancies. The aim of this study was to determine the relationship between the expression of MUC1, MUC2, MUC5AC and MUC6 in cholangiocarcinoma and clinicopathological parameters as well as patient survival. In addition, this study was performed to identify whether immunohistochemical staining for mucins is useful to differentiate cholangiocarcinoma from adenocarcinoma of the pancreas and gallbladder. Immunohistochemical staining for MUC1, MUC2, MUC5AC and MUC6 was performed for 85 cases of cholangiocarcinoma, including 34 cases of intrahepatic cholangiocarcinoma (ICC), 51 cases of extrahepatic cholangiocarcinoma (ECC), 11 cases of gallbladder adenocarcinoma and 14 cases of pancreas adenocarcinoma. For cholangiocarcinomas, positivity of immunohistochemical staining for MUC1, MUC2, MUC5AC and MUC6 was 65.8, 23.5, 61.1 and 14.1%, respectively. For cholangiocarcinomas, MUC1 positivity was determined to be statistically significant for poor differentiation (p=0.002), T category (p=0.003), gross type (ICC, p=0.005; ECC, p=0.006) and poor patient survival (p=0.015). MUC5AC was more frequently expressed in advanced tumors (p=0.013). MUC6 expression was significantly detected in well-differentiated cholangiocarcinomas (p=0.006). There was no significant difference for the mucin staining patterns of cholangiocarcinomas, pancreatic adenocarcinomas and gallbladder adenocarcinomas. These results indicate that MUC1 expression in cholangiocarcinomas is closely related to dedifferentiation, infiltrative growth pattern and patient survival. Our results suggest that the expression of MUC1 might be associated with the progression of cholangiocarcinoma.