Introduction: Many Authors already described automatic activity arising from accessory pathways, but the underlying mechanism has not been clarified yet. They may be due to embryogenetic features of myocardium or may be related to specific excitability during radiofrequency ablation. Methods and results: we report the case of a man who underwent an accessory pathway ablation in WPW Syndrome. At the end of the procedure we found an accelerated rhythm originating at the insertion of the accessory pathway. Conclusion: If this manifestation represents the effect of thermal injury or if it is a real intrinsic automaticity is not fully documented.