Objective: The distribution of the two estrogen receptors (ER–α, ER–β) in human prostate tissue have not been fully clarified, so the present study investigated the mRNA expression of the receptors to explain the broad spectrum of estrogen activity in prostate cancer. Materials and Methods: Four human prostate cancer cell lines (LNCap, JCA–1, DU–145 and PC–3) and 24 pairs of untreated prostate cancer tissue and noncancerous tissue from resected prostate glands were subjected to RT–PCR testing. Results: Both LNCap and JCA–1 expressed the mRNA of both receptors, but DU–145 and PC–3 only expressed ER–β mRNA. In the human prostate tissue samples, 20 of the 24 prostate cancer tissues expressed ER–α, and 23 of the 24 expressed ER–β. Of the 24 noncancer tissues, 14 expressed ER–α mRNA and 17 expressed ER–β mRNA. The incidence of ER–β mRNA expression between the paired cancer and noncancer tissues was statistically significantly different (p<0.05). Conclusions: A higher incidence of ER–β mRNA expression in untreated prostate cancer tissues was observed. Furthermore, the absence of ER–α mRNA and the presence of ER–β mRNA expression in hormone–independent and/or untreated prostate cancer cells leads to a tentative speculation of the mechanism of the hormone refractory feature of prostate cancer.