Evidence accumulated to date indicates that inhibition of the rennin-angiotensin system with angiotensin receptor blockers (ARB) may prevent new-onset of diabetes. ARB is also used for the prevention of occurrence and progression of complications in diabetes and diabetic nephropathy. From the results of recent large-scale clinical studies, ARB is considered as a first choice drug in hypertensive patients with diabetes. In this review article, we focus on the effects of ARB on progression and prevention against diabetes as a metabolic-improving agent.