AV nodal reentry tachycardia (AVNRT) is the most common cause of paroxysmal supraventricular tachycardia. Radiofrequency ablation is today the treatment of choice. Aim: To report our experience in patients who underwent slow pathway ablation. Patients and methods: Fifty six consecutive patients (68% female, mean age 43 years old) that underwent slow pathway ablation are reported. Results: Sixty four percent of patients had failed drug therapy. During electrophysiological study, AVNRT was induced in 55 patients. Isoproterenol was required for induction in 36%. Programmed atrial stimulation revealed dual AV nodal pathway in only 64% of the patients; 29% had AVNRT with single nodal curve and 7% only prolongation of AH interval. The slow pathway was ablated in 55 patients. One patient refused ablation because of risk of AV block. All patients had immediate success post ablation. Sixty four percent of patients persisted with partial evidence of dual curve manifested by sudden AH prolongation and single echoes. Conclusions: Isoproterenol is essential for ruling out AVNRT, since 29% of the patients had baseline single nodal curve and in only 64% was tachycardia induced without isoproterenol. Persistence of residual dual physiology does not rule out the success of ablation (Rev Méd Chile 2003; 131: 1237-42)