The acute hemodynamic and humoral responses to intravenous dilevalol (10 to 390 mg) were evaluated in 10 patients with moderate hypertension. Dilevalol, in doses of 30 mg or more, decreased arterial pressure (p < 0.0001) through a decrease in total peripheral resistance (p < 0.0001) associated with an increase in stroke volume and cardiac output (p < 0.0001). Heart rate increased moderately at doses above 190 mg. Plasma norepinephrine levels increased (p < 0.05), but epinephrine levels remained unchanged. Plasma renin activity and level of atrial natriuretic peptide decreased (p < 0.01 and p < 0.01, respectively). The hypotensive and humoral changes persisted 3 hours after the last dose. Dilevalol modified the pattern of hemodynamic response to isometric stress, slightly enhancing the increases in peripheral resistance and blunting increases in cardiac output and heart rate. The response in arterial pressure during administration of dilevalol remained similar to that seen in the pretreatment phase. The results show that dilevalol, when given intravenously in a dose of 30 to 90 mg, reduces arterial pressure by reducing total peripheral resistance without acceleration in heart rate. On the basis of these hemodynamic effects, dilevalol should be further evaluated for treatment of hypertensive emergencies.