Background: Electroanatomical mapping system (CARTO) is a method that reconstructs a three dimensional map of the heart by sequentially acquiring contacted catheter electrographic data. It improves catheter navigation and the three dimensional display of an arrhythmia mechanism. We report an early experience of radiofrequency catheter ablation (RFCA) for ventricular arrhythmia by electroanatomical mapping(EAM) compared to conventional mapping(CM). Methods and Results: From February 2000 to May 2003, out of twenty five patients(9 male, age 38.9짹13.7) who had ventricular arrhythmia, 12 patients underwent conventional mapping guided RFCA(group A) and 13 patients underwent electroanatomical mapping guided RFCA(group B). Average symptom duration was 75.9짹86.3 months. EAM was usually done during arrhythmia to acquire an activation map. CM was done using a pace map or activation map depending on the arrhythmia. 5 patients in group B had a history of failed CM guided RFCA. Other results are as follows; Conclusion: In group B, disease entity was more diverse and complex than group A. EAM was found effective guiding RFCA of ventricular arrhythmia. Because EAM was mainly activation time map and because of early experience, mean fluoroscopic time was longer in group B. If experiences were accumulated, the procedure time would be decreased and EAM would be an effective method for RFCA of ventricular arrhythmia.