Background: it is not easy to create a transmural lesion with a conventional RF ablation catheter at thick myocardial region such as left ventricle. This study was performed to explore the efficacy of novel magnetic bipolar device in comparison with conventional unipolar or bipolar RF ablation. Methods: Neodymium magnets (0.5T) assembled in ablation catheters were used to facilitate tissue contact in a bipolar RF ablation system. In vitro sheets of porcine skeletal muscle with 10-mm thickness were ablated with a 4-mm tip unipolar RF ablation catheter (UA), bipolar ablation system using a pair of 4-mm tip catheters (BA), and magnetic bipolar system (MB). RF generator setting was 50W and 90째C, and RF energy was delivered for 60 seconds. One side of a skeletal-muscle sheet was exposed to saline with 37째C and flow of 37 cm/s mimicking LV endocardial surface. Another side of a sheet was exposed to air mimicking epicardial surface. Five ablation lesions were created in each condition. Ablated tissues were fixed with 10% formalin and lesion dimensions were measured. Results: Table describes the results of the study. Conclusion: Novel magnetic bipolar RF ablation system creates more transmural lesion and larger lesion volume. This system could be used for VT ablation or linear ablation in AF treatment.