Transcatheter modification of the AV node with radiofrequency energy (RF) was performed in 6 patients (mean age 24 years) with inducible AV node reentry tachycardia (AVNRT). Although tachycardia could be controlled with antiarrhythmic drugs in each patient, the option was offered to eliminate the arrhythmia by means of RF catheter technique. A 7F catheter with 2 mm interelectrode distance and a large tip electrode was positioned to record the maximal His deflection, then withdrawn until the smallest possible His and ventricular potentials with a large atrial signal could be recorded. RF energy was delivered at this site in unipolar mode in incremental steps, until AVNRT was no longer inducible or VA block occurred. The procedure resulted in non-inducibility of tachycardia in 5/6 patients. The fast and the slow pathways were abolished in 2 and 1 patients, respectively, while the AV node duality persisted in 2 in spite of non-inducibility. VA block occurred in 2 patients, while the anterograde conduction was preserved in all. During the follow-up (mean 4.5 months) 5/6 patients remained free of AVNRT without drugs. It is concluded that transcatheter RF modulation of the AV node can be advised, provided that similar results will be obtained in larger series with longer follow-up, as the first line therapy in patients with AVNRT.