SummaryThe mechanisms, clinical presentation and therapy of supraventricular tachycardias are discussed.The therapy has changed from palliation by means of anti-arrhythmic drugs into definitive cure by ablation of the arrhythmia substrate.Radiofrequency energy causes tissue damage by heating and appears to be a safe method for catheter ablation of supraventricular tachycardias.We report a 97% success rate for radiofrequency ablation of 195 accessory atrioventricular pathways thereby curing these patients from circusmovement tachycardia and paroxysmal atrial fibrillation. Complications occurred in 3% of patients.One hundred seventy-two patients with atrioventricular nodal reentrant tachycardia, caused by reentry within dual AV-nodal pathways, were treated by selectively ablating one of the pathways with non-inducibility of the arrhythmia afterwards in 97% of the cases. Nine percent of patients had a recurrence but were succesfully treated in a second session. The procedure was complicated by complete AV-block in 4% of paitients.The disappointing medical treatment of atrial fibrillation and the fact that atrial fibrillation can be the cause of a reversible form of heart failure (tachycardiomyopathy), induced the clinical application of alternative forms of treatment. Ablation of the normal atrioventricular conduction system by using radiofrequency energy was performed with a 100% success rate in 121 patients. After implantation of a ventricular pacemaker it is possible to control and regularize the ventricular rhythm leading to rate control and amelioration of ventricular performance.