The presence of persistent microalbuminuria in IDDM is strongly predictive of the future development of end stage renal failure and of cardiovascular disease to a lesser extent. Screening for microalbuminuria is an essential component of modern diabetes practice, as effective antihypertensive therapy, and particularly, the use of angiotensin converting enzyme inhibitors is of proven benefit in retarding progression of renal disease. Cost benefit analysis justifies the expense of microalbuminuria screening programmes and early intervention. It has been estimated that the use of angiotensin converting enzyme inhibitors in microalbuminuric IDDM will save 5200 Pounds-11,000 Pounds per year of life saved. Angiotensin converting enzyme inhibitors are not free of side-effects, and it is therefore essential, given the intrinsic variability of the albumin excretion rate, and the regression to normoalbuminuria of a significant proportion of patients, to confirm the diagnosis of microalbuminuria by repeated measurements prior to the commencement of treatment. The value of intensive glycaemic control is unproven, and further prospective studies are required. There are no proven therapies for the prevention of macrovascular disease in IDDM, although the value of cessation of smoking and aggressive blood pressure control are undoubted in the non-diabetic population. Controversy persists about the value of lipid lowering therapy, especially in young patients, although even in this group there is an increased risk of cardiovascular disease. Microalbuminuria is the strongest known predictor of cardiovascular disease in NIDDM; in contrast to the situation in the non-diabetic population, active lipid lowering therapy is not of proven cardiac benefit, but intervention seems justifiable when taken in the context of the very high prevalence of cardiovascular disease. Microalbuminuria is also predictive of end stage renal disease in NIDDM. Although intervention with angiotensin converting enzyme inhibitors has not been proven to prevent end stage renal disease, stabilisation of albumin excretion rate and creatinine clearance have been demonstrated in normotensive NIDDM, and it seems likely that longer term follow-up studies will confirm the benefit of angiotensin converting enzyme inhibitors in the prevention of end-stage renal disease. The observed predictive power of microalbuminuria as regards both cardiac and renal risk in NIDDM when considered in conjunction with the preliminary results of the benefits of angiotensin converting enzyme inhibition lend further support to the employment of microalbuminuria screening in NIDDM.