Objective: To investigate the expressions of atypical protein kinase C ι subtype (aPKC-ι) and E-cadherin in chol- angiocarcinoma, and analyze molecular mechanisms of the invasion and metastasis of cholangiocarcinoma. Methods: The expressions of aPKC-ι and E-cadherin in 9 specimens of benign bile duct tissues and 35 specimens of cholangiocarcinoma were detected by EnVision immunohistochemistry, and their correlations to the clinicopathologic characteristics and invasion of cholangiocarcinoma were analyzed. Results: The positive rate of aPKC-ι was significantly higher in cholangiocarcinoma than in benign bile duct tissues (68.6% vs. 11.1%, P = 0.006), while the positive rate of E-cadherin was significantly lower in cholangiocarcinoma than in benign bile duct tissues (37.1% vs. 88.9%, P = 0.016). aPKC-ι expression was negatively cor- related to E-cadherin expression (r = -0.287, P < 0.05). aPKC-ι expression was positively and E-cadherin expression was negatively correlated to the differentiation and invasion of cholangiocarcinoma (P < 0.05). Conclusion: The expressions of aPKC-ι and E-cadherin may reflect the differentiation and invasive potential of cholangiocarcinoma. As a polar regulation-as- sociated protein, aPKC-ι may play an important role in the invasion and metastasis of cholangiocarcinoma. Objective: To investigate the expressions of atypical protein kinase C ι subtype (aPKC-ι) and E-cadherin in chol-angiocarcinoma, and analyze molecular mechanisms of the invasion and metastasis of cholangiocarcinoma. Methods: The expressions of aPKC-ι and E- cadherin in 9 specimens of benign bile duct tissues and 35 specimens of cholangiocarcinoma were detected by EnVision immunohistochemistry, and their correlations to the clinicopathologic characteristics and invasion of cholangiocarcinoma were analyzed. Results: The positive rate of aPKC-ι was significantly higher in cholangiocarcinoma than in benign bile duct tissues (68.6% vs. 11.1%, P = 0.006) while the positive rate of E-cadherin was significantly lower in cholangiocarcinoma than in benign bile duct tissues (37.1% vs. 88.9%, P = 0.016) -I expression was negatively cor- related to E-cadherin expression (r = -0.287, P <0.05). aPKC-expression was positively and E-cadherin expression was negatively correlated to the di differentiation and invasion of cholangiocarcinoma (P <0.05). Conclusion: The expressions of aPKC-ι and E-cadherin may reflect the differentiation and invasive potential of cholangiocarcinoma. As a polar regulation-as-associated protein, aPKC-ι may play an important role in the invasion and metastasis of cholangiocarcinoma.