Since a low prevalence of cancer in hypertensive patients receiving angiotensin converting enzyme inhibitors was reported, a biological action of angiotensin II (Ang-II) on the development or progression of cancer has been drawn attention. Recently, a widespread use of AT1 receptor blockers (ARBs) has contributed more attractive information on the involvement of Ang-II in cancer. Interestingly, there is increasing evidence that the renin -angiotensin system is implicated in the development of various cancers. From basic and clinical data, we believe that ARB has a novel ability to decelerate prostate specific antigen elevation especially in hormone refractory cancer and suppress the incidence of prostate cancer, which implies that ARB may have a chemopreventive activity for prostate cancer.