Catheter ablative techniques have assumed an increasingly important role in the treatment of patients with drug-refractory cardiac arrhythmias. Catheter ablation of the AV junction is considered the procedure of choice for management of patients without bypass tracts with drug-resistant supraventricular arrhythmias. Catheter techniques have been used with increasing frequency in attempts to ablate accessory AV tracts. These techniques currently appear to be less effective than surgical techniques but involve less morbidity and expense. In some centers, accessory pathway ablation using catheter techniques is the procedure of first choice in selected patients with drug-refractory tachycardia mediated by an accessory pathway. Catheter ablation of ventricular tachycardia should be reserved for patients with mappable ventricular tachycardia who are not candidates for cardiac electrosurgery or insertion of an automatic defibrillator. The development of more flexible catheters and more manageable energy delivery systems holds promise for more effective catheter techniques.