BACKGROUND Radiofrequency (RF) catheter ablation currently is used for treatment of cardiac arrhythmias. Although the success rate is high for almost all supraventricular tachycardias (SVT), this technique has some drawbacks, especially when pulmonary veins (PV) are targeted for treatment of atrial fibrillation (AF). Additionally, new techniques for isolation of the PVs have the drawback that they can be used only for PV isolation and not for routine treatment of other SVTs. The aim of this study was to report on the safety and efficacy of a new cryoablation system for treatment of all SVTs. RESULTS Forty-nine patients with SVT (38 men; age 48 years, range 23-76) were enrolled in the study. Five patients were withdrawn from the study before they underwent cryoablation. The remaining 44 patients were treated with cryoablation (22 AF, 15 atrial flutter, 3 accessory pathway, 2 AV nodal reentrant tachycardia, 1 AV junction ablation for permanent AF, 1 atrial tachycardia). Cryoablation was performed with the CryoCor cryoablation system, which uses a precooling system and N2O as a refrigerant. The number of freezes applied varied according to the index arrhythmia treated. Successful isolation of PVs was performed in 20 of (96%) 21 AF patients and 53 of 55 veins. The overall acute success was 98% (43/44). Fifty-three PVs were isolated (2.5/patient). The success rate was 100% (23/23) for right-sided procedures. The average and nadir temperatures reached in right-sided and left-sided procedures were -77 degrees C and -80 degrees C and -75 degrees C and -78 degrees C, respectively. No acute PV stenosis was seen. CONCLUSIONS This novel cryoablation system appears to be safe and can successfully treat different types of SVTs, including AF. Isolation of PVs is possible without producing stenosis. Despite the high blood flow in the right atrial isthmus and PVs, bidirectional conduction block can be achieved.