Although cavotricuspid isthmus radiofrequency catheter ablation is considered curative therapy for typical atrial flutter, many patients develop an atrial fibrillation after ablation. The purpose of our study was to determine the incidence and the predictive factors of post-ablation atrial fibrillation. One hundred and forty eight consecutive patients underwent cavotricuspid isthmus ablation for the treatment of typical atrial flutter between January 2004 and December 2005 in our electrophysiological department. Complete cavotricuspid isthmus block was successfully obtained in 96.6% of the patients. At the end of the electrophysiological study a sustained atrial fibrillation was inducible in 20 patients (13.5%). During an average follow-up of 21.3 +/- 8.2 months, atrial fibrillation occurred in 27% of the patients. Univariate analysis identified four parameters correlated with post-ablation atrial fibrillation among the 21 parameters tested: the young age of the patients, a prior history of atrial fibrillation, an inducible atrial fibrillation, and a paroxysmal atrial flutter. Only inducible atrial fibrillation and paroxysmal atrial flutter were independent factors linked to atrial fibrillation after ablation. In our study the incidence of atrial fibrillation after cavotricuspid isthmus radiofrequency catheter ablation is 152 per 1,000 patient-years, i.e. 25 times higher than the incidence of atrial fibrillation in the general population of the same age. Twenty five percent of the patients who had neither prior history of atrial fibrillation nor structural heart disease suffered from atrial fibrillation during a mean follow-up of 21.3 +/- 8.2 months. All these results suggest that atrial flutter and fibrillation could be manifestations of a more general electrophysiologic disease. They emphasize the need for all these patients to benefit from regular, long-term cardiological follow-up after cavotricuspid isthmus ablation because of the high incidence of atrial fibrillation. Treatment with antiarrhythmic and antithrombotic agents should also be adapted to these factors.