Candesartan cilexetil is a newly synthesized, specific angiotensin II type 1 receptor antagonist. Candesartan cilexetil is a prodrug, and is converted to its active form, candesartan, by the enzyme esterase at the time of intestinal absorption. We conducted a single-dose study to evaluate the effect of candesartan cilexetil on cardiac hemodynamics and hormone response in 13 patients with congestive heart failure. Mean blood pressure did not show any significant change in the patients receiving either 2 or 8 mg. Pulmonary capillary wedge pressure was reduced by 34.9% in the patients given 8 mg of candesartan cilexetil. The cardiac index did not show any significant changes. Total peripheral vascular resistance was reduced in the patients receiving 2 or 8 mg from 1 h after administration, and the tendency to decrease continued until 8 h after administration. Plasma atrial natriuretic peptide levels were reduced by 15.5% 2 h after dosing with 8 mg of candesartan cilexetil. Plasma brain natriuretic peptide levels decreased slightly after dosing with candesartan cilexetil. Administration of candesartan cilexetil reduces cardiac preload and afterload and is expected to be useful for the treatment of congestive heart failure.