Decreased E-cadherin expression in tumor cells has been suggested to promote tumor invasiveness. We examined E-cadherin expression in 30 cases of endometrial carcinoma by immunohistochemistry using a monoclonal antibody to E-cadherin and investigated its correlation with other histopathologic features of the tumor. We observed that: (1) E-cadherin expression decreased with loss of differentiation (P < 0.05); (2) E-cadherin expression was inversely correlated with depth of myometrial invasion (P < 0.05); (3) decreased E-cadherin expression was correlated with paraaortic node metastasis (P < 0.01); and (4) multivariate analysis comparing the depth of myometrial invasion to the pattern of E-cadherin expression, histologic grade, nuclear grade, and lymph-vascular space invasion showed that the depth of myometrial invasion was most strongly correlated with decreased E-cadherin expression (P < 0.005). These findings seem to be consistent with the concept that the dissociation of cancer cells due to decreased expression of E-cadherin facilitates invasion of tumor cells.