Radiofrequency (RF) catheter ablation has been widely used in the treatment of cardiac arrhythmias. In atrioventricular nodal reentrant tachycardia (AVNRT), the experience has been predominantly in adults. The cardiac electrophysiological records of 18 consecutive children undergoing RF catheter AV node modification for AVNRT were reviewed. The patients (10 females, 8 males) were 8.2-17.9 years of age (mean 13.6 +/- 3.0), weight 15.2-88.1 kg (mean 52.2 +/- 20.8), and height 103-190 cm (mean 157.1 +/- 21.7). Thirteen were on antiarrhythmic medications (1-3, average 1.5 drugs/day). All drugs were discontinued 48 hours prior to the ablations. The procedures were performed under sedation and local anesthesia. Pre- and post-AV node modification electrophysiological studies were performed in all procedures. The 18 patients underwent a total of 25 procedures (1.39 +/- 0.61 per patient): the anterior approach aimed at the antegrade fast pathway in the first four patients and the posterior approach aimed at the slow pathway in the remainder. The number of energy applications was 8-54 (19.8 +/- 10.7) per procedure. The maximum energy used in each procedure was 30-50 watts (33.8 +/- 8.4). The average energy was 24-50 watts (33.0 +/- 6.8). The fluoroscopy time was 7.1-73.4 minutes (29.9 +/- 20.0) per procedure, for a total catheterization time of 228-480 minutes (300.3 +/- 59.1). Preablation spontaneous or induced AVNRT (cycle length 310.4 +/- 55.0 msec) was seen in all except one who had the arrhythmia (cycle length 270 msec) on surface ECG.(ABSTRACT TRUNCATED AT 250 WORDS)