In patients with advanced chronic heart failure, characterised by prolonged QRS duration and impaired cardiac contractility, decreasing dyssynchrony by biventricular pacing seems to improve exercise tolerance (6-min walk distance), symptoms (New York Health Association class) and quality-of-life scores. Although the results of several reports have been consistent, the numbers of patients studied were small, and many of the changes were trends that did not reach statistical significance. The availability of a non-pharmacological treatment that improves exercise capacity and quality of life would be a major advance. However, further studies will need to address the question of mortality and morbidity benefits of such intervention.