The advent of the ACE inhibitors has been one of the major developments in cardiovascular pharmacology this century. Aside from their role as potent anti-hypertensive drugs with few adverse effects, ACE inhibitors have numerous other effects that have only been partially explained. Antihypertensive therapy is the most effective treatment in patients with diabetic nephropathy, postponing the development of end-stage renal failure. Although this effect can apparently be obtained with all antihypertensives (except nifedipine), recent meta-analyses have indicated that the beneficial effects of ACE inhibitors on proteinuria and preserved renal function are greater than with other drugs. In nondiabetic patients, treatment with ACE inhibitors may delay or prevent the development of congestive heart failure following acute myocardial infarction. Whether this also occurs in diabetic patients is still unknown, but subgroup analysis of existing studies and controlled clinical trials in this area should be encouraged. In conclusion, ACE inhibitors are the only drugs that have been proven, in controlled clinical trials, to be effective in preventing progression from micro-albuminuria to overt nephropathy. Furthermore, they are more effective in diminishing albuminuria at low levels of blood pressure reduction compared with other antihypertensives. In comparison with beta-blockers, ACE inhibitors have the advantage that they do not mask the subjective symptoms of hypoglycaemia, nor do they affect the serum lipid profile.