Background: Noninducibility with burst pacing after ablation for atrial fibrillation (AF) has been commonly used for an end point of the procedure. Early recurrence of AF (ERAF) immediately after AF ablation has been used to find triggers for AF. This prospective randomized study compared the clinical efficacy between inducibility and ERAF as an end point after ablation in patients with paroxysmal AF. Methods: 83 patients with paroxysmal AF were randomly assigned to 2 groups. After pulmonary vein (PV) isolation, ERAF immediately after electrical cardioversion under high dose (10 關g/min) of isoproterenol administration (group A) and induction test by burst pacing (group B) were performed, respectively. Elimination of non-PV foci was performed in group A. If there was reproducible indicibility in group B, additional ablation guided by CFAE was performed. All tests were repeated three times. Results: Baseline characteristics are the same between two groups (mean age 55.2짹14.0 vs. 55.9짹10.0 years, male 81.0% vs. 78%, mean LA size 37.6짹5.0 vs. 39.7짹5.2 mm). After PV isolation, additional ablation was done in 21 patients (50%) in group A and 19 patients (46.3%) in group B, respectively (p=0.739). Total procedure times were significantly longer in group B compared with group A (250.3짹89.4 min vs 214.2짹61.8 min, p=0.048). During the short-term follow up after 3 months of blanking period, the rate of freedom from recurrence was significantly higher in group B compared with group A (95.1% vs 81.0%, p=0.047), and Kaplan-Meier analysis also showed that the success rate following the procedures was significantly higher in group B than in group A (p=0.045, by Log-rank test). Conclusion: During the short-term follow-up, evaluation of noninducibility with burst pacing was more effective as an end point after ablation for paroxysmal AF compared with test of ERAF following cardioversion under isoproterenol infusion. Larger number of the patients with longer follow-up period are warranted to confirm these results.