Treatment with beta blockers results in improvement in functional status, and reduces mortality in patients with heart failure. A number of differences in the results noted could be due to additional properties of the specific beta blockers studied: absence of cardioselectivity, and existence of a vasodilator effect and of an associated antioxidant effect. We studied the effects of celiprolol, a cardioselective beta blocker with a stimulant effect on beta2 receptors. One hundred thirty-two patients presenting with chronic heart failure of various etiologies, with an ejection fraction of <40% and New York Heart Association cardiac functional status grades II and III were included in a randomized, double-blind, placebo-controlled study. The maximum dose of celiprolol (100 mg) was attained after 1 month. The study lasted 1 year. The primary evaluation criterion was functional class as evaluated using the Goldman questionnaire. There was no difference in efficacy between the 2 treatment groups in terms of functional class (p = 0.56). With regard to the secondary evaluation criteria, an improvement in DiBianco functional score was seen with celiprolol (p = 0.03), as well as a significant reduction in heart rate (p = 0.01). Ejection fraction increased in both groups (p = 0.15). There was no difference regarding improvement in left ventricular volume as determined at echocardiography or in exercise capacity. The safety profile of celiprolol was excellent. There was no difference in terms of cardiovascular mortality (2 receiving celiprolol vs 4 placebo), onset of arrhythmias (2 receiving celiprolol vs 3 placebo), worsening of heart failure (26 receiving celiprolol vs 23 placebo), or noncardiovascular adverse events (9 receiving celiprolol vs 14 placebo). The absence of a significant efficacy of celiprolol, a beta blocker with vasodilator properties, but exerting stimulation of beta2 receptors, suggests an unfavorable role of this latter property in heart failure. However, the safety profile of celiprolol was excellent. This beta blocker may consequently be used for its other indications, hypertension and angina, in patients presenting with altered cardiac function.