Backgroud : magnetic navigation system (MNS) ( Niobe, stereotaxis, Saint-Louis, Missouri, USA ) allows remote control of a radiofrequency ablation catheter using a steerable magnetic field and a catheter advancement system. We report our initial experience of ablation of arrhythmias using MNS. Methods : a total of 12 arrythmias (11 patients; mean age 58 years; 7 women ) had an electrophysiologic study followed by ablation with the MNS ( Niobe II, Stereotaxis ) using non-irrigated 4 mm-tip catheters with three distal magnets( Celsius RMT, Biosense Webster ). All patients were symptomatic, with commonly-accepted indications for ablation: atrioventricular nodal re-entrant tachycardia( AVNRT, n=4; typical atrial flutter, n=2; AVRT, n=5; Ventricular tachycardia, n=1 ). Results : ablation was performed successfully in 9 ( 81% ) patient without any complication. In 2 patients ( 18% ), MNS technique was unsuccessful: one atrial flutter, one double tachycardia ( AVRT and VT ); In these cases, success was obtained by switching to the manual technique. total procedure time was 115짹81 minutes ( AVNRT 97짹39, AVRT 94짹41, Atrial flutter 98짹60 ); Total fluoroscopy time was 24짹22 minutes( AVNRT 21짹13, AVRT 21짹9, Atrial flutter 11짹8 ).; mean number of radiofrequency current ablations was 18짹 24 ( AVNRT 8짹2, AVRT 4짹2 , Atrial flutter 39짹46 ). Conclusion : MNS ablation is a feasible treatment for various arrhythmias, with a high success rate. However, further improvement is required to achieve a higher successful rate for treatment of atrial flutter.