Backgrounds: Booster RF catheter ablations(RFCA) in addition to successfully performed ablations can provide better and more effective treatments and prevention of recurrence for atrioventricular nodal reentrant tachycardia(AVNRT). However, studies weighing the benefits of booster RFCA in the prevention of recurrence and its potential adverse effects are still inconclusive. In this study, we sought to investigate additional effect of booster RFCA during slow pathway ablation in patients with AVNRT. Methods : This study was performed from 2001 to 2004 on a total of 408 typical AVNRT (156 men and 252 women; mean age, 4516 years) who underwent slow pathway ablations. Procedural success was defined as no inducible AVNRT or single echo after isoproterenol provocation test. Booster RFCA was defined as ablation after procedural success. Booster RFCAs were performed on 236 patients and the control group consisted of 172 patients. Total time of RFCA, mean time of procedure, recurrence, and AV conduction impairment rate were compared between the two groups. Results: The mean number of booster RFCA for the booster group was 2.442.89. The total time of RFCA (272.78193.50 sec vs 221.63132.50 sec; p=0.0096) and mean time of procedure (80.4629.23 min vs 68.0520.46 min; p<0.001) were statistically larger in booster group. However, the difference in the recurrence rate (1.28% vs 1.75% ; p=0.70) and AV block rate (0.42% vs 0.58%; p=0.82) were statistically insignificant between the two groups. Conclusions: Booster RFCA did not provide a more effective treatment nor lower rates of recurrence for AVRNT patients in this study. In fact, booster RFCAs elongated the time of RFCA and the time of procedure.