OBJECTIVE : This study aimed to evaluate efficacy, safety, and long-term outcome of radiofrequency catheter ablation (RFCA) for atrial tachyarrhythmia (ATa) in patients with atrial septal defect (ASD). METHODS : Seventy-five ASD patients with ATa (52% atrial fibrillation, AF) were enrolled. Electrophysiological study and RFCA were performed, with endpoints of index and multiple procedures as follows: (a) atrial tachycardia/atrial flutter (AT/AFL), absence of inducibility of any atrial arrhythmia and (b) AF, circumferential pulmonary vein ablation (CPVA, paroxysmal AF), bidirectional block of lines, and disappearance of complex fractionated atrial electrograms (persistent and long-standing persistent (LSP)-AF). RESULTS : Cumulative success rate at 1-year follow-up was 79.9% and dropped to 59.0% at a median follow-up of 63 months (range, 14-114 months) for multiple procedures (mean 1.6 ± 0.7 [1-3]). Freedom from ATa after multiple procedures was achieved in 75% patients with AT/AFL and 43.6% patients with AF (P = 0.006 for comparison). In multivariate analysis, older age at ASD correction (HR, 1.033 [95% CI, 1.008-1.059]; P = 0.01), ASD diameter before correction (HR, 1.054 [95% CI, 1.006-1.105]; P = 0.027), and first-diagnosed ATa type (AF; HR, 2.25 [95% CI, 1.03-4.92]; P = 0.042) were significant independent predictors of ATa recurrence. Patients with more risk factors had higher risk of ATa recurrence. CONCLUSIONS : The long-term outcome of RFCA for ATa outcome was favorable for AT/AFL while mediocre for AF. ATa recurrence was more common in patients with older age at ASD correction, larger ASD diameter before correction, and first-diagnosed AF. Patients with more risk factors had higher ATa recurrence risk.