Roughly 40% of all diabetics, whether insulin dependent or not, develop persistent albuminuria, a decline in their glomerular filtration rate, and elevated blood pressure, i.e., diabetic nephropathy. Diabetic nephropathy is the single most important cause of end-stage renal disease in the Western world, accounting for over one-quarter of all end-stage renal disease. Systemic/glomerular hypertension plays a role in the initiation and progression of diabetic glomerulopathy. Angiotensin-converting enzyme (ACE) inhibitors are superior to conventional antihypertensive drugs in preventing the development of glomerular lesions in insulin-treated streptozotocin diabetic rats. Lowering of glomerular hypertension may be the crucial factor involved. Human studies suggest that ACE inhibitors postpone the progression to clinical overt diabetic nephropathy in normotensive diabetic patients with persistent microalbuminuria. ACE inhibitors combined with a diuretic reduce albuminuria and postpone renal insufficiency in hypertensive diabetics with overt nephropathy. No treatment modality other than antihypertensive treatment has yet been proven to be effective in protecting renal function in diabetic nephropathy. All previous reports dealing with the natural history of diabetic nephropathy have demonstrated a cumulative death rate between 50 and 77% 10 years after the onset of proteinuria. Effective antihypertensive treatment has reduced the cumulative death rate to 15-20% 10 years after the onset of nephropathy.