BACKGROUND AND OBJECTIVES: Radiofrequency catheter ablation (RFCA) of accessory pathways (AP) has recently become the choice of therapeutic regimen for the patients with atrioventricular (AV) reentrant tachycardia. Among AP, anteroseptal AP is subject to the potential complication of inadvertent AV block during RFCA because of the close proximity to the AV node-His bundle conduction system. This study was conducted to evaluate the efficacy and safety of RFCA of anteroseptal AP at the atrial site by ablation catheter introduced through left subclavian vein. MATERIALS AND METHODS: Seven patients with orthodromic AV reentrant tachycardia mediated by a retrogradely conducting anteroseptal AP were studied. Antidromic AV reentrant tachycardia was also induced in one patient during electrophysiologic study. Mean age was 24+/-10 years (range, 16-42 years) and the male to female ratio was 5:2. APs were manifested in 4 patients and concealed in 3 patients. After diagnosis of anteroseptal AP by electrophysiologic study, temperature guided radiofrequency current was applied in the anteroseptal area at the atrial site of tricuspid annulus by a steerable ablation catheter. RESULTS: All pathways were successfuly ablated. The AV node or His bundle conductions was not impaired in any patients. There were no complications related to the procedure. CONCLUSION: RFCA of the anteroseptal AP at the atrial site by a ablation catheter introduced through superior vena cava is effective and safe with good preservation of the normal conduction system.