Ramipril is a second generation angiotensin converting enzyme (ACE) inhibitor. Like enalapril, it is a prodrug and is hydrolysed in vivo to release the active metabolite, ramiprilat, which has a long elimination half-life, permitting once-daily administration. The antihypertensive efficacy of ramipril has been confirmed in large-scale noncomparative studies conducted in general practice as well as in more rigorously controlled clinical trials. In the former, approximately 85% of patients with mild to moderate essential hypertension have responded successfully to treatment with ramipril 2.5 or 5 mg/day, while comparative trials indicate that the antihypertensive efficacy of the drug is equivalent to that of other established ACE inhibitors and the beta-adrenoceptor antagonist atenolol. As expected, the response rate to ramipril monotherapy is lower in patients with severe hypertension (around 40%), although the blood pressure lowering effect can be enhanced with the addition of a diuretic such as hydrochlorothiazide or piretanide. The antihypertensive efficacy of ramipril is maintained in patients with diabetes mellitus and preliminary data indicate that the drug has the beneficial effect of decreasing urinary albumin excretion in diabetic patients with nephropathy. Ramipril is superior to atenolol in causing regression of left ventricular hypertrophy, although the clinical significance of this effect per se remains to be established. The large-scale Acute Infarction Ramipril Efficacy (AIRE) study demonstrated that ramipril 5 or 10 mg/day significantly decreased the risk of all-cause mortality by 27% in patients with clinical evidence of heart failure after acute myocardial infarction, even if transient. The beneficial effect of ramipril was apparent by 30 days of treatment and appeared to be greatest in patients with more severe ventricular damage after infarction. Ramipril is well tolerated in general practice, with 5% or fewer patients discontinuing therapy because of drug intolerance. The data available suggest that ramipril shares a similar tolerability profile to that of other established ACE inhibitors. Thus, clinical data confirm ramipril as a useful alternative ACE inhibitor for the treatment of patients with mild to moderate hypertension, and indicate a beneficial effect of the drug in patients with clinical evidence of heart failure after acute myocardial infarction. It is also reasonable to assume that ramipril will be of value in the treatment of patients with more established heart failure or asymptomatic left ventricular dysfunction.