The effect of catheter ablation of the atrioventricular junction (AV) and implantation of a rate-adaptive pacemaker on quality of life and exercise capacity was evaluated prospectively in 12 consecutive patients with paroxysmal atrial fibrillation (AF). All patients had been demonstrated to have paroxysmal AF that was refractory to medical therapy over a long period of time (mean 9 +/- 7 years). Patients performed a symptom-limited treadmill exercise test on the day before catheter ablation and 6 weeks after hospital discharge. Quality of life was measured using the physical dimension of the McMaster Health Index Questionnaire and the Psychological General Well-Being Index before and 6 weeks after ablation. There were no serious complications related to catheter ablation or permanent pacemaker implantation. All patients remain in complete AV block with a completely paced rhythm at a mean follow-up of 8 +/- 2 months. The McMaster Health Index scores increased from a mean of 0.69 +/- 0.20 before to 0.92 +/- 0.14 after ablation (p = 0.002). The mean Psychological General Well-Being score improved from 59.8 +/- 14.8 at baseline to 84.9 +/- 13.6 6 weeks after discharge (p = 0.001). Treadmill exercise duration increased from 6.4 +/- 4.6 to 9.9 +/- 2.6 minutes (p = 0.03) and correlated strongly with changes in functional capacity measured with the McMaster Health Index (r = 0.70, p = 0.03). These results suggest that catheter ablation of the AV junction and implantation of a rate-adaptive pace-maker significantly improve the quality of life and exercise capacity of patients with paroxysmal AF refractory to medical therapy.