Background:It has been known that ACEI/ARB is effective to prevent atrial fibrillation(AF) in high risk patients. However, we don���t know whether it is effective to prevent the recurrence of AF after radiofrequency ablation. Methods and subjects: 152 patients(Mean age : 57짹10 yrs, M:F=94:58) performed AF ablation due to drug refractory paroxysmal(Mean age : 57짹10yrs, M:F=58:43) or persistent AF (Mean age : 56짹10yrs , M: F=36:15)were enrolled. We compared the recurrence rate between the groups divided by the use of ACEI/ARB in paroxysmal and persistent AF respectively. Mean follow-up duration was 18짹14 months.Results:1.In whole subjects, the overall recurrence rate after ablation therapy was 26% (N= 39). 2. Recurrence rate was significantly decreased in the group with the use of ACEI/ ARB in persistent AF patients(12.1 vs 61.1%, p<0.01) but this difference was not observed in paroxysmal AF patients(24.2 vs 22.9%, p=0.87). 3. In persistent AF, LA size (44.2짹8.4mm, 44.3짹5.8 , p=0.45) and ejection fraction (62 짹6.5%, 61.5짹6.2%, p=0.28) were not significantly different between the patients with and without recurrence. 4. In multivariate analysis, the use of ACEI/ARB was independently associated with recurrence after adjusting LA size and ejection fraction(p<0.01, odds ratio(95% confidence interval) : 0.078(0.02-0.35)).Conclusion:ACEI/ARB was found to be effective to prevent AF recurrence after catheter ablation in persistent AF patients.