OBJECTIVE Transcatheter aortic valve replacement (AVR) is a promising approach to aortic valve disease. The implications of this new therapy are not entirely known. We describe the potential for the development of new atrioventricular (AV) block. BACKGROUND Atrioventricular block is a known complication of conventional surgical AVR. Block is presumed to occur as a consequence of surgical trauma to the cardiac conduction tissue during excision of the diseased aortic valve and débridement of the calcified annulus. Whether AV block might occur as a consequence of nonsurgical implantation of an aortic stent valve is unknown. METHODS We reviewed our experience with patients undergoing transcatheter AVR using both the percutaneous transarterial and the open-chest direct left ventricular apical ventriculotomy approaches. Patients were considered at high risk for conventional surgery because of comorbidities. Continuous arrhythmia monitoring was performed for at least 48 h after the valve implantation procedure. Patients who developed apparently new, clinically significant AV block were identified. RESULTS Transcatheter AVR was successfully performed in 123 patients. Seventeen of these patients (13.8%) had pre-existing permanent pacemakers. Two patients (1.6%) required pacemaker implantation because of pre-existing intermittent bradycardia. Seven patients (5.7%) developed new and sustained complete AV block requiring pacemaker implantation. An additional 4 patients (3.3%) developed new and sustained left bundle branch block but did not require pacemaker implantation. CONCLUSIONS As with conventional AVR surgery, transcatheter AVR may result in impaired atrioventricular conduction. Physicians and patients should be aware of the potential for AV block and pacemaker dependence.