ObjectiveTo review recent studies on the roles of estrogen receptor β in breast cancer. MethodsThe literatures in recent years on the biological function, variant isoforms of estrogen receptor and its possible roles in breast cancer were reviewed. ResultsERβ was a new member of the superfamily of steroid receptors, it might play an important role in breast tumor genesis, tumor progression, prognosis and reaction to the endocrine therapy in breast cancer. ConclusionERβ is a new prognostic marker in breast cancer.