Recently non-pharmacological therapies for atrial fibrillation (AF) have been developed. The electrophysiological mechanisms of AF is thought to be the development of multiple reentrant wavelets circulating around anatomic barriers and variable regions of functional conduction block responsible of the perpetuation of the arrhythmia. Also the role of the triggering foci has been highlighted. To cure AF by means of non pharmacological therapy we may eliminate and/or modify the substrate. To better understand the mechanism underlying the AF and to choose the best ablation strategy is of fundamental importance to map the right and the left atrium during AF. Our experience shows that in chronic idiopathic AF disorganized atrial activity is observed at all atrial regions while in paroxysmal idiopathic AF the left septum and the right atrial posterior areas are highly disorganized while the lateral region shows more organized atrial electrical activity. Multipolar basket catheters are extremely useful in mapping right and left atrium in order to guide the best ablation strategy.