In North America and Western Europe, diabetic nephropathy is the commonest cause of renal failure requiring renal replacement therapy. Glomerular filtration rate normally declines with increasing age. The decline in glomerular filtration rate observed in hypertensive patients with diabetic nephropathy can be limited by adequate control of blood pressure with conventional therapy. In hypertensive diabetic patients with nephropathy or microalbuminuria, angiotensin-converting enzyme inhibitors have specific renoprotective effects in addition to their hypotensive activity. Normotensive patients with microalbuminuria also benefit from angiotensin-converting enzyme inhibitors, probably because this group of patients are relatively hypertensive when measured using 24 h ambulatory blood pressure monitoring. Good glycaemic control will reduce the incidence of microalbuminuria, but its role in progression of microalbuminuria to overt nephropathy is controversial. These issues are discussed in the context of optimal care for patients with diabetic renal disease.