OBJECTIVE To explore the relationship between the E-cadherin catenin complex and invasiveness of pituitary adenoma. METHODS The expression of E-cadherin catenin complex was determined by immunohistochemistry in 78 cases of human pituitary adenomas including invasive adenoma 44 cases, noninvasive adenoma 34 cases and the relativity of their expressions with hormone-producing, pituitary apoplexy and necrosis or cystoid change, tumor diameter were analyzed. RESULTS The invasive group had a significantly lower expression of E-cad and alpha-cat than that of noninvasive group (chi-squared = 13.969, P < 0.01). There was no statistical significance for beta-cat expression between the invasive group and noninvasive group (chi-squared = 0.430, P > 0.05). Moreover, the expressions of beta-cad and alpha-cat were significantly lower in macro-adenoma group than that in micro-adenoma group (chi-squared = 5.038, P < 0.05). The expression of E-cad was significantly lower in endocrine inactive group than that in endocrine active group (chi-squared = 4.614, P < 0.05). The expression of beta-cat was significantly lower in the group with apoplexy and necrosis than that in the group without apoplexy and necrosis (chi-squared = 6.701, P < 0.05). CONCLUSIONS The reduction of E-cad catenin complex is related to invasiveness and clinical pathological characteristics.