Objectives. The purpose of this study was to determine the safety and efficacy of radiofrequency ablation as definitive therapy for primary atrial tachycardias. Background. Primary atrial tachycardias are often difficult to control with antiarrhythmic medications and frequently require nonpharmacologic interventions for definitive therapy. Despite isolated reports of successful treatment of primary atrial tachycardias with radiofrequency ablation, the safety and efficacy of this technique have not been established in a larger series with long-term follow-up. Methods. The immediate procedural success rate, associated complications and follow-up data of radiofrequency ablation were evaluated in 15 consecutive patients (11 adults and 4 children) with primary atrial arrhythmias that were refractory to medical management. Results. The clinical arrhythmia was ectopic atrial tachycardia in 11 patients and sinus node reentry in 4. The site of origin of the tachycardia was in the right atrium in 14 patients and in the left atrium in 1 patient (with two distinct foci) where the local atrial electrogram preceded the onset of the P wave by 10 to 30 ms. Radiofrequency energy successfully terminated the primary atrial tachycardia in each of the patients, and all were discharged from the electrophysiology laboratory in sinus rhythm without inducible atrial tachycardia. A mean of 10.8 ± 9.9 radiofrequency applications were delivered using 30 W of power for 30 s. The local intracardiac activation time (relative to the P wave in the surface electrocardiogram) was a mean of -21 ± 5 ms at the successful ablation site and -15 ± 6 ms at unsuccessful sites (p < 0.001). No complications were observed, although one patient with incessant ettopic atrial tachycardia had sinus pauses after ablation. During a mean follow-up period of 277 ± 133 days, the clinical arrhythmia recurred in three patients (20%, 95% confidence intervals 3% to 37%) including two patients with ectopic atrial tachycardia and one patient with sinus node reentry. One of these patients was successfully treated in a second ablation session. Conclusions. Thus, radiofrequency catheter ablation appears to be a safe and effective technique for the treatment of primary atrial arrhythmias that are refractory to antiarrhythmic medications. © 1993.