The utility of selective radiofrequency catheter ablation of the slow pathway for the treatment of common and uncommon atrioventricular nodal reentrant tachycardia (AVNRT) was studied in 110 consecutive patients, 94 with slow-fast form common AVNRT, and 11 and 5, respectively, with the fast-slow and slow-slow forms of uncommon AVNRT. Ablation sites were determined by mapping a late and spiky "slow pathway potential" in the posterior right atrial septum in common AVNRT, and also the earliest retrograde atrial activation over the retrograde slow pathway in uncommon AVNRT. AVNRT was successfully eliminated in all patients with a mean number of radiofrequency pulses of 2.9 +/- 3.0 and a mean total energy applied of 3536 +/- 2996 joules. There were no early or late complications, except for transient AV block for 15 sec immediately after energy application in one common AVNRT patient, and no recurrence of AVNRT in a mean follow-up period of 24 +/- 13 months. There were no significant differences between common and uncommon AVNRT in success rate, mean application number and total energy applied. However, the AVN physiology post-ablation was different. Slow pathway conduction was eliminated in only 32% of the patients post-ablation in common AVNRT, while it was elininated in 100% in uncommon AVNRT. Selective radiofrequency catheter ablation of the slow pathway can cure common and uncommon AVNRT effectively and safely. Common AVNRT can be eliminated irrespective of the persistence of slow pathway conduction, while uncommon AVNRT can be eliminated by the eradication of slow pathway conduction.