Diabetic nephropathy is a clinical syndrome characterized by persistent albuminuria (> 300 mg/24 h), a relentless decline in glomerular filtration rate, and elevated systemic blood pressure. The prevalence of an abnormally elevated albumin excretion rate (> 30 mg/24 h) is approximately 40% in patients with both insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). Diabetes has become the leading cause of end-stage renal failure in the United States and Japan and it is still the second leading cause in Europe. Identification of patients at high risk of developing diabetic nephropathy is possible by screening for microalbuminuria (30 to 300 mg/24 h). Randomized controlled trials in normotensive IDDM and NIDDM patients with persistent microalbuminuria indicate that angiotensin-converting enzyme (ACE) inhibitors diminish urinary albumin excretion rate and postpone or may even prevent progression to clinically overt diabetic nephropathy. These findings suggest that screening and intervention programs are likely to have life-saving effects and lead to considerable economic savings. High blood pressure is an early and frequent phenomenon that can accelerate the course of diabetic nephropathy. Besides ACE inhibitors, conventional antihypertensive treatment (mainly beta-blockers and diuretics) reportedly reduce albuminuria and diminish the loss of kidney function in IDDM patients with diabetic nephropathy. The same beneficial effect has been demonstrated using ACE inhibition combined with diuretics in hypertensive IDDM patients with overt nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)