Incorrect lead selection and unexpected ECG artifact during an attempted resuscitation after inhospital cardiac arrest resulted in undetected lack of cardiac monitoring for approximately 13 minutes. The patient was finally countershocked and regained a spontaneous pulse but was determined to have experienced profound neurologic damage and died shortly after being extubated. This type of failure may be common, particularly with older monitor/defibrillators. Caregivers, health care organizations, and device manufacturers should be aware of this potential problem and institute preventive measures.