In this article we emphasize the need for prompt intervention in diabetic patients with high blood pressure in order to protect the heart, brain, kidney, and the vascular tree against arteriosclerotic damage, which is the main cause of mortality in type 1, and particularly type 2 diabetes mellitus. Recent placebo-controlled, randomized trials indicate that compared with the nondiabetic population, a lower blood pressure threshold for intervention and a lower target blood pressure are adequate in terms of target organ protection. Although all major classes of antihypertensive drugs have demonstrated a potential benefit in treating diabetic hypertensive patients, blocking the renin-angiotensin system with angiotensin converting enzyme (ACE) inhibitors is especially useful in patients at high risk for myocardial infarction and/or renal damage. The new class of antihypertensive agents that block the angiotensin II receptor have renal effects very close to those observed with ACE inhibitors. The potential role of this new class in the treatment of hypertension in diabetes will depend on the results of ongoing trials.