Background: Recently, it has been reported that continuation of warfarin (W) throughout atrial fibrillation (AF) ablation without switching to heparin (H) is relevant and safe. We hypothesized that continuous warfarininzation (CW) strategy maintains more stable international normalized ratio (INR) during peri-procedural period without increase of complication as compared with classical strategy switching to heparin (SH). Methods: We compared CW strategy (n=20) and SH strategy (n=43) in 63 patients who underwent radiofrequency catheter ablation (RFCA) of AF (47 male, 5512 years old, paroxysmal AF : persistent AF=48:15). In CW group, we continued W before RFCA maintaining INR>1.5. In SH group, we stopped W 3 days before procedure and switched to low molecular weight H or unfractionated H. During procedure, optimal activated clotting time (ACT; 350~400) was maintained with intravenous H. We compared H requirement during RFCA, post-ablation INR, and peri-procedural complication between CW and SH strategies. Results: 1. The pre-procedural INR was higher in CW group (2.06짹0.36) than in SH group (1.11짹0.14, P<0.001). 2. During RFCA, the intravenous H requirement was significantly lower in CW group (1797짹919 U/30 min) vs. than in SH group (3002짹876 U/30 min, P<0.001) to maintain optimal ACT. 3. After RFCA, the proportions of patients with optimal INR (2~3) were higher in CW group compared with SH group (1st post-procedure day 85% vs. 7%, p<0.001; 2nd post-procedure day 90% vs. 30%, P<0.001; 3rd post-procedure day 100% vs. 30%, p<0.001). 4. However, the incidence of acute hemorrhagic complication, groin hematoma, tended to be higher in CW group than in SH group (30% vs. 9%, P=NS). There was no ischemic thromboembolic complication in both groups. Conclusion: In patients with AF ablation, the peri-procedural continuation of warfarin was easy to use and to maintain optimal INR with lower dose of intra-procedural intravenous heparin compared with classical strategy switching to heparin. However, attention to the risk of bleeding complication may be required.