The activity of the renin-angiotensin-aldosterone system (RAAS) is elevated both in the circulation and in the renal tissue of diabetic and nondiabetic nephropathies. The increased RAAS activity plays an important role in the hemodynamic and nonhemodynamic pathogenetic mechanisms involved in kidney disease. Previous studies have demonstrated that albuminuria is not only a marker of glomerular lesions, but also a progression promoter, and finally a powerful predictor of the long-term beneficial effect of blood pressure-lowering therapy. Randomized crossover and parallel blind studies in patients with diabetic nephropathy have demonstrated that angiotensin II receptor blockers (ARB) induce favorable changes in systemic blood pressure, renal hemodynamics, and proteinuria similar to those induced by angiotensin-converting enzyme (ACE) inhibition. Studies have revealed the optimal renoprotective dose for some ARBs; however, additional dose titration studies are urgently needed to obtain the maximum benefit of this valuable new class of compounds. The combination of ARB and ACE inhibition is well tolerated and even more effective than monotherapy in reducing systemic blood pressure and albuminuria in diabetic nephropathy. In addition, dual RAAS blockade is safe and well tolerated. Impaired autoregulation of glomerular filtration rate (GFR); demonstrated with some blood pressure-lowering agents implies disturbances in the downstream transmission of the systemic blood pressure into the glomerulus, leading to capillary hypertension or hypotension depending of the level of blood pressure. ARB does not interfere with GFR autoregulation in hypertensive diabetic patients. In contrast to previous observational studies with ACE inhibition, long-term treatment with ARB has similar beneficial renoprotective effect on progression of diabetic kidney disease in hypertensive diabetic patients with ACE II and DD genotypes. ARB can prevent/delay development of diabetic nephropathy independently of its beneficial blood pressure-lowering effect in patients with type 2 diabetes and microalbuminuria. Recently, two landmark studies led to the following conclusion: "Losartan and Irbesartan conferred significant renal benefit in patients with type 2 diabetes and nephropathy. This protection is independent of the reduction in blood pressure it causes. The ARB is generally safe and well tolerated." A recent metaanalysis indicates that ARBs reduce cardiovascular events mainly because of reduction in first hospitalization for congestive heart failure in hypertensive type 2 diabetic patients with albuminuria. The studies mentioned here suggest that ARB represents a beneficial treatment of hypertension and proteinuria in incipient and overt diabetic nephropathy.