Catheter ablation techniques have become an accepted treatment form for a variety of supraventricular arrhythmias. After the introduction of radiofrequency energy, catheter ablation has become the first line of treatment and has replaced surgery in patients with the preexcitation syndromes. The success rate in large series is very high, while the complication rate in experienced hands is very low. Despite all this progress, the ablation of a small subset of accessory atrioventricular pathways poses some problems. The ideal source of energy is still unknown and improvement in catheter technology are needed. This review will try to focus on some of these issues dealing with a very exciting area of clinical cardiology.