Background -The purpose of this study was to determine the radiation exposure during catheter ablation of atrial fibrillation(AF) using the pulmonary vein(PV ) approach. Methods and Results -The study included 15 patients with AF and 5 p atients each with atrial flutter and atrioventricular nodal reentrant tachycardi a(AVNRT) who underwent fluoroscopically guided procedures on a biplane X-ray sy stem operated at a low-frame pulsed fluoroscopy(7.5 frames per second). Radiati on exposure was measured directly with 50 to 60 thermoluminescent dosimeters (TL Ds). Peak skin doses(PSDs), effective radiation doses, and risk of fatal maligna ncies were all computed. Mean fluoroscopy durations for AF procedures were 67.8 ±21 minutes in the right anterior oblique(RAO) and 61.9±16.6 minutes in the le ft anterior oblique(LAO) projection, significantly different from that required for atrial flutter and AVNRT. The mean PSDs measured with the TLDs were 1.0±0.5 Gyinthe RAO and 1.5±0.4 Gy in the LAO projection. The lifetime risk of excess f atal malignancies normalized to 60 minutes of fluoroscopy was 0.07%for women an d 0 .1%for men. Conclusions-The relatively small amounts of the patient’s radiati on exposure in this study, despite the prolonged fluoroscopy durations, can be a ttributed to the use of very-low-frame pulsed fluoroscopy, the avoidance of ma gnification, and optimal adjustments of the fluoroscopy exposure rates. The resu lting lifetime risk of fatal malignancy is within the range previously reported for standard supraventricular arrhythmias. Background -The purpose of this study was to determine the radiation exposure during catheter ablation of atrial fibrillation (AF) using the pulmonary vein (PV) approach. Methods and Results-The study included 15 patients with AF and 5 p atients with atrial flutter and atrioventricular nodal reentrant tachycardi a (AVNRT) who underwent fluoroscopically guided procedures on a biplane X-ray sy stem operated at a low-frame pulsed fluoroscopy (7.5 frames per second). Radiati on exposure was measured directly with 50 to 60 thermoluminescent dosimeters Mean fluoroscopy durations for AF procedures were 67.8 ± 21 minutes in the right anterior oblique (RAO) and 61.9 ± 16.6 minutes in (TLs) The le ft anterior oblique (LAO) projection, significantly different from that required for atrial flutter and AVNRT. The mean PSDs measured with the TLDs were 1.0 ± 0.5 Gyinthe RAO and 1.5 ± 0.4 Gy in the LA The lifetime risk of excess f atal malignancies normalized to 60 minutes of fluoroscopy was 0.07% for women an d 0 .1% for men. Conclusions-The relatively small amounts of the patient’s radiati on exposure in this study, despite the prolonged fluoroscopy durations, can be a ttributed to the use of very-low-frame pulsed fluoroscopy, the avoidance of ma gnification, and optimal adjustments of the fluoroscopy exposure rates. The resu lting lifetime risk of fatal malignancy is within the range previously reported for standard supraventricular arrhythmias