Radiofrequency (RF) catheter ablation has been proposed as a treatment of atrial fibrillation (AF). Several approaches have been reported and success rates have been dependent on procedural volume and operator's experience. This is the first report of a multicenter study of RF ablation of AF. We treated 44 men and 25 women with paroxysmal (n = 40) or persistent (n = 29), drug refractory AF. Circular pulmonary vein (PV) ostial lesions were deployed transseptally, during sinus rhythm (n = 42) or AF (n = 26), under three-dimensional electroanatomic guidance. Cavo-tricuspid isthmus ablation was performed in 27 (40%) patients. The mean procedure time was 215 +/- 76 minutes (93-530), mean fluoroscopic exposure 32 +/- 14 minutes (12-79), and mean number of RF pulses per patient 56 +/- 29 (18-166). The mean numbers of separate PV ostia mapped and isolated per patient were 3.9 +/- 0.5, and 3.8 +/- 0.7, respectively. Major complications were observed in 3 (4%) patients, including pericardial effusion, transient ischemic attack, and tamponade. At 1-month follow-up, 21 of 68 (31%) patients had had AF recurrences, of whom 8 required electrical cardioversion. After the first month, over a mean period of 9 +/- 3 (5-14) months, 57 (84%) patients remained free of atrial arrhythmias. RF ablation of AF by circumferential PV ostial ablation is feasible with a high short-term success rate. While the procedure and fluoroscopic exposure duration were short, the incidence of major cardiac complications was not negligible.