Acute effects of coronary vasodilators (nifedipine, nicardipine, and nitroglycerin) on atrial natriuretic peptide (ANP) and the renin-angiotensin-aldosterone system were studied in normal subjects and patients with essential hypertension. Nifedipine lowered blood pressure both in normal subjects and in patients and elevated ANP, plasma renin activity, and angiotensin II in normal subjects but not in hypertensive patients. Nicardipine lowered blood pressure but failed to elevate ANP and angiotensin II in normal subjects. Nitroglycerin failed to elevate ANP in normal subjects.