The renin-angiotensin system is responsible for renovascular hypertension resulting from narrowing of the renal arteries. Inhibitors of angiotensin-converting enzyme (ACE) interrupt the conversion of angiotensin I to angiotensin II, causing a reduction in blood pressure. Several drugs of this family have been introduced since captopril was launched, including enalapril, lisinopril, ramipril and others. While they are effective antihypertensive agents, they can in some cases lead to deterioration of renal function, especially in patients with bilateral renal artery stenosis or stenosis of a solitary kidney. ACE inhibitors must also be administered with caution to sodium-depleted patients. Calcium antagonists, presumed to be ideal for the treatment of low renin hypertension, have also proved to be effective in patients with renal artery stenosis, many of whom have severe refractory hypertension. These agents, in common with ACE inhibitors, may be useful for determining the lateralisation index used to establish the kidney responsible for hypertension.