The long-term hemodynamic effects of a new beta-adrenoceptor blocker, bunitrolol, were evaluated in 11 men with untreated essential hypertension in WHO stage I. Oxygen consumption, heart rate, cardiac output (Cardiogreen), and intraarterial brachial pressure were recorded at rest in supine or sitting position and during steady-state work at 300, 600, and 900 kpm/min. After the subjects were treated with bunitrolol (dose 10–60 mg/day) as the sole drug for one year, the hemodynamic study was repeated. Treatment reduced the mean arterial pressure 15% at rest supine, 13% at rest sitting, and 10–14% during exercise. The heart rate was decreased 13% at rest supine, and 17–21% during exercise. There was no increase in the stroke volume, and the cardiac index was reduced 17% at rest supine, 23% at rest sitting, and 24–28% during exercise. Treatment did not significantly change the total peripheral resistance at rest, but significantly diminished the decrease in this value observed during exercise prior to therapy. No serious side effects were seen, but two subjects developed sleep disturbances, which disappeared when bunitrolol was given as one dose in the morning instead of twice daily. The major hemodynamic, long-term effects of bunitrolol in mild and moderate essential hypertension resemble those seen with other beta-adrenoceptor blockers like alprenolol, atenolol, metoprolol, and timolol. The study does not support the assumption that bunitrolol causes less depression in cardiac output than do other beta-adrenoceptor blockers.