OBJECTIVES: This study was performed to compare the long-term clinical efficacy of treatment with metoprolol versus carvedilol in patients with chronic heart failure. BACKGROUND: Beta-adrenergic blockade is of proven value in chronic heart failure. Metoprolol, a selective beta-blocker, is widely used, but recent trials suggest carvedilol, a nonselective beta-blocker with alpha-1-receptor antagonist activity and antioxidant activities, is also effective. It is uncertain, however, if these additional properties of carvedilol provide further clinical benefit compared with metoprolol. METHODS: In this randomized double-blind control trial, 51 patients with chronic heart failure and mean left ventricular (LV) ejection fraction of 26% +/- 1.8% were randomly assigned treatment with metoprolol 50 mg twice daily or carvedilol 25 mg twice daily in addition to standard therapy after a four-week dose titration period for a total of 12 weeks. Response was assessed by a quality of life questionnaire, New York Heart Association class, exercise capacity (6-min walk test), radionucleotide ventriculography for LV ejection fraction, two-dimensional echocardiography measurement of LV dimensions and diastolic filling and 24-h electrocardiograph monitoring to assess heart rate variability. RESULTS: Both carvedilol and metoprolol produced highly significant improvement in symptoms (p < 0.001), exercise capacity (p < 0.05) and LV ejection fraction (p < 0.001), and there were no significant differences between the two drugs. Carvedilol had a significantly greater effect on sitting and standing blood pressure, LV end-diastolic dimension and normalized the mitral E wave deceleration time. CONCLUSIONS: Both metoprolol and carvedilol were equally effective in improving symptoms, quality of life, exercise capacity and LV ejection fraction, although carvedilol lowers blood pressure more than metoprolol.