Renal vascular resistance is increased in essential hypertension, with a consequent reduction in renal plasma flow together with a normal or slightly reduced glomerular filtration rate. Non-specific vasodilators may exacerbate this effect while loop diuretics, beta-blockers, angiotensin converting enzyme inhibitors and calcium antagonists may increase these renal hemodynamic parameters. We studied the effect of lacidipine, a new long-lasting calcium antagonist, on renal hemodynamics in 11 essential hypertensives. Lacidipine (4 mg once a day) acutely increased renal plasma flow without affecting the glomerular filtration rate. A transient, but non-significant, diuresis and natriuresis occurred. After 4 weeks of lacidipine treatment, all the parameters of renal function returned to basal levels. These results suggest that the well known renal effects of calcium antagonists are, at least in part, related to the onset of the antihypertensive effect being more pronounced with compounds such as nifedipine which have a rapid-onset, blood pressure-lowering effect.