Background The aim of this study is to evaluate the usefulness of P-Wave Signal-Averaged Electrocardiogram (P-SAECG) in predicting the recurrence of Atrial Fibrillation (AF) after successful pulmonary vein isolation(PVI). Materials and Methods From Feb 2009 to March 2011, 32 drug-refractory AF patients who underwent PVI at our institute were enrolled (paroxysmal AF=23; 8, persistent AF) retrospectively. AF recurrence was defined as any atrial tachyarrhythmia documented during follow-up period, except first 3months after the PVI. The patients were divided into group 1 with recurrence (n=11) and group 2 without it (n=21). A P-SAECG was recorded at 1-day after PVI and followed up at 3-months. We analyzed P-SAECG parameters such as filtered and unfiltered P-wave duration, value of root-mean square voltage (terminal in 20, 30, and 40 ms, respectively), P-wave area and signal averaged P-wave morphology on 3 axes. The signal averaged P-wave morphology was divided into typical and atypical types. Baseline characteristics and echocardiographic findings were analyzed, too. Results Baseline characteristics showed no differences between 2 groups. Among the analyzed parameters on P-SAECG, initial filtered P-wave duration was longer in group 1 ( 156.36짹51 Group 1 vs. 133.20짹13.43, p=0.002 ). On multivariate analysis, initial FPD >130 ms (p=0.045, HR 4.056, C.I. 1.031 to 15.45) and atypical P wave morphology (p=0.043, HR 4.272, C.I. 1.044 to 17.39), Left atrial volume index >30ml/m2 (p=0.036, HR 6.597, C.I. 1.134 to 38.35) were a prognostic predictors for recurrence, but persistent AF, the left atrial dimension were not predictors for recurrence. Conclusions The Signal-Averaged P-Wave duration might be prognostic marker for recurrence of AF with successful PVI. More large clinical study will be needed. Key Words : Atrial fibrillation, Signal-Averaged P-Wave, Pulmonary vein isolation