Introduction: It has been demonstrated that right atrium (RA) plays an important role in atrial fibrillation (AF) maintenance and termination of persistent AF (PeAF) can be achieved by radiofrequency catheter ablation (RFCA) at the RA in some patients. However, it remains unclear which patients need additional RA ablation as an incorporated approach for (long-lasting) PeAF. We hypothesized that continuous fractionated electrograms at the RA (RA-CFE) during AF predict clinical outcome and guide triage of good candidate for bi-atrial ablation before the procedure. Methods: Eighty-eight consecutive patients (56.3짹10.1 years of age) undergoing catheter ablation of PeAF were studied. In 46 patients, RFCA was directed at only linear lesion or defragmentation of the LA after pulmonary vein isolation (LA ablation). RA electrograms-guided substrate modification were sequentially performed if AF persisted after that (bi-atrial ablation, n=42). Subsequent atrial tachycardias (AT) were mapped, and ablation was attempted. Procedural end point was termination or noninducibilty of AF. RA-CFE on the intracardiac electrograms were assessed in both group before the procedure. Results: RA-CFE before ablation was observed in 23 (50%) of the patients in whom end point was achieved by LA ablation alone and in 33 (78.6%) among the patients who needed bi-atrial ablation. There was no significant difference in rate of acute termination between patients with RA-CFE and those without RA-CFE following LA ablation (78.3% vs 73.9%, p=0.730) and bi-atrial ablation (36.4% vs. 44.4%, p=0.658), respectively. During the mean eight-month, rates of freedom from recurrence of AF or AT were 71.7% in LA ablation and 71.4% in bi-atrial ablation (p=0.974). However, the rate of freedom from recurrence following bi-atrial ablation was significantly higher in patients with RA-CFE than in those without RA-CFE (81.8% vs 33.3%, p=0.004), while there was no significant difference in the success rates between those with RA-CFE(+) and RA-CFE(-) in the patients who underwent LA ablation alone (65.2% vs 78.3%, p=0.326). RA-CFE was associated with the success rate after bi-atrial ablation (HR 8.869, 95% CI:1.662 to 47.324; p=0.011). Conclusions: Additional RA ablation provides an increment in the efficacy among patients with PeAF who showed RA-CFE before the procedure. The RA-CFE identified by visual inspection can predict which patients require further RA ablation following PVI and extensive LA ablation.