Both androgens and estrogens play a significant role in the prostate and are critical for normal prostate growth and development. The role of androgens in the prostate and in prostate disease is well known, however, the role for estrogens in the prostate and in prostate disease is complex and is still only just beginning to be appreciated. Our understanding of the role and action of estrogens in the prostate has advanced significantly recently due to important discoveries, including the discovery of a second estrogen receptor subtype (ER-β), the detection of aromatase in the prostate, and the identification of rapid nongenomic estrogen signaling. We now know that estrogens are essential for normal tissue homeostasis within the prostate and that too little or too much leads to perturbation of the glands growth and the emergence of disease. We are also beginning to recognize the importance and differential roles of the estrogen receptors ER-α and ER-β. Specifically, the activation of ER-α leads to aberrant proliferation, inflammation, and the development of premalignant lesions, while, in contrast, the activation of ER-β is critical in prostatic stromal−epithelial cell signaling and mediating antiproliferative effects that balance the proliferative action of androgens on the epithelia. These data have established the importance and complexity of estrogen action. We now know that estrogens have the capacity to exert both beneficial and adverse effects in the prostate via ER-β and ER-α, respectively. Based on this, the selective targeting of estrogen action may form the basis of new therapies for prostate disease.