Pacemakers and implantable cardiac defibrillators (ICDs) are widely used for the management of cardiac arrhythmias and congestive heart failure (CHF). Acute implantation complication rates range from 3% to 7%. The aim of this study is to describe the incidence of lead perforation on computed tomography (CT), and correlate these findings with electrophysiologic data. Images of 100 consecutive patients with permanent pacemakers (n = 72) or ICDs (n = 28) who underwent multidetector CTs of the chest were identified. Cases were reviewed by 2 cardiothoracic radiologists, and a third if there was disagreement. Each CT was reviewed for device and fixation type, tip position, and presence of pericardial effusion. Results were correlated with lead impedance and pacing threshold, when available [79% (79/100)]. A cardiac electrophysiologist interpreted device data. All 100 patients had right ventricular leads (58 passive, 42 active) and 61 had right atrial leads (12 passive, 49 active). 15% (15/100) of patients had a lead perforation. Perforation rates were 15% (9/61) for atrial and 6% (6/100) for ventricular leads (P < 0.05, chi square). Four of 28 (14%) right ventricular ICD leads and 2 of 72 (3%)right ventricular pacemaker leads were perforated (P < 0.05, chi square). 12% (6/49) of active right atrial leads, and 25% (3/12) of passive right atrial leads perforated (P = NS, chi square). 7% (3/42) of active right ventricular leads, and 5% (3/58) of passive ventricular leads perforated (P = NS, chi square). Electrophysiologic parameters did not differ significantly between perforated and nonperforated leads. Asymptomatic perforation is a common phenomenon and rarely resulting in electrophysiologic consequences. Atrial leads perforated more frequently than ventricular leads, and ventricular ICD leads perforated more frequently than ventricular pacemaker leads.