In the United States, physicians adapt currently available defibrillators to accommodate leads for biventricular pacing in those congestive heart failure patients who might benefit from cardiac resynchronization and who are additionally at risk for sudden cardiac death. The adaptation of the lead system of available defibrillators to also allow them to function as biventricular pacemakers presents occasions in which inappropriate shocks are delivered due to double counting of the right and left ventricular depolarizations by the implantable cardiac defibrillator. We reviewed a series of inappropriate shock deliveries that occurred after the implantation of biventricular pacing cardiac defibrillators at our institution; all of these shocks were related to ventricular double counting. Each had different underlying causes and management strategies. Complications such as these emphasize the importance of attentiveness to ventricular channel electrograms and to device sensing with the use of biventricular pacing cardiac defibrillators. In addition, a thorough working knowledge of pacemaker and defibrillator operation is essential for the prediction and correction of inappropriate therapies.