To assess the impact of biventricular pacing on quality of life over 12 months of follow-up, 76 patients in the MUSTIC trial were evaluated by 2 instruments: The Minnesota Living with Heart Failure Questionnaire and the Karolinska Quality of Life Questionnaire. MUSTIC is a randomized, controlled study to evaluate the effects of biventricular pacing in patients in New York Heart Association class III heart failure with intraventricular conduction delay. Following a single, blind, crossover comparison of 3 months of biventricular pacing to inactive pacing (sinus rhythm group) or ventricular-inhibited pacing (atrial fibrillation group), 85% of patients preferred and were programmed to biventricular pacing and were followed for 12 months. In parallel with clinical improvements, substantial benefits in quality of life for most broad domains of quality of life and cardiovascular symptoms were found during biventricular pacing already within the crossover phase with a maintained benefit over the 12-month follow-up. Biventricular pacing improved quality of life in patients with heart failure and intraventricular conduction delays. The benefits were sustained over 12 months of follow-up.