This study reports on the acute and long-term results of cryoablation in patients with supraventricular and ventricular tachycardia. One hundred fifty nine patients with cardiac arrhythmias (147 with supraventricular and 12 with ventricular tachycardia) were consecutively enrolled in our institution to undergo trnasvenous cryoablation with a new cryotechnology system (CryoCor trade mark ). This cryoablation system consists of a console, an articulating arm housing a pre-cooler, and a disposable sterile steerable bipolar 10-fr catheter. The N(2)O is used as a main refrigerant. The acute and chronic outcomes (after 15 months for patients with supraventricular tachycardia and 9 months for patients with ventricular tachycardia) were comparable to those using radiofrequency energy. From this study we concluded that transvenous cryoablation is a safe and effective therapy for the treatment of cardiac arrhythmias.