E-cadherin is a calcium-dependent, epithelial cell adhesion molecule. It has recently been implicated as a tumor suppressor. This review article contains a description of the structure, function, and regulation of E-cadherin and other members comprising the cadherin family. In particular, we discuss studies concerning the ability of estrogens to modulate E-cadherin levels in vivo. Finally, we consider the hypothesis that estrogens may promote breast, uterine and ovarian cancer by down-regulating E-cadherin levels in these tissues.