The prostate is a major accessory organ of the male mammalian reproductive system, with structural and functional activities under the control of androgens. The prostate comprises three compartments, differentiated by the cytokeratin expression profile. The basal cells express predominantly high molecular weight cytokeratins (CK5 and CK14); the luminal secretory cells express predominantly low molecular weight cytokeratins (CK8 and CK18); and finally the intermediate cells express a combination of basal and luminal cytokeratins. Additionally, there is increasing evidence that basal epithelial cells differentiate into luminal epithelial cells. Prostate cancer is one of the most common cancers affecting men and it has a high morbidity and mortality rate. Human Prostate Epithelial Cells provide unique opportunities to study many important features of the prostate, as well as, chemical and hormonal carcinogenesis.