Biventricular pacing has been introduced to treat patients with end-stage heart failure, and short-term results of this technique are promising. Because data on longer follow-up are limited to 3-month follow-up, the sustained effect of biventricular pacing is unclear and long-term survival is unknown. Forty patients with end-stage heart failure in New York Heart Association (NYHA) functional class III or IV with left ventricular (LV) ejection fraction (EF) <35%, QRS duration >120 ms, and left bundle branch block morphology received a biventricular pacemaker. At baseline, and at 3 and 6 months after implantation, the following parameters were evaluated: NYHA class, Minnesota quality-of-life score, QRS duration on surface electrocardiogram, 6-minute walking distance, and LVEF. Long-term follow-up was obtained for up to 2 years. All clinical parameters improved significantly at 3 months and remained unchanged at 6-month follow-up. LVEF increased from 24 +/- 9% to 34 +/- 11%. Before implantation, patients were hospitalized (for congestive heart failure) an average of 3.9 +/- 5.3 days/year compared with 0.5 +/- 1.5 days/year after implantation. Long-term follow-up showed a survival of 87.5% at 2 years. Thus, biventricular pacing resulted in improvement of symptoms and quality of life, accompanied by improvement in 6-minute walking distance and LVEF. These effects were observed at 3 months after implantation and were maintained at 6-month follow-up. Moreover, 2-year survival was excellent.