Automated external defibrillators (AEDs) play a key role in the community resuscitation of persons with cardiac arrest and are of proven clinical benefit. Although AEDs are complex medical devices designed to function during life-threatening emergencies, little is known about their reliability. To determine the number and rate of AED recalls and safety alerts, to identify trends in these rates, and to identify the types of malfunctions prompting AED and AED accessory advisories. Analysis of weekly US Food and Drug Administration (FDA) Enforcement Reports between January 1996 and December 2005 was performed to identify all recalls and safety alerts (collectively referred to as "advisories") involving AEDs and AED accessories. Confirmed AED device malfunctions were identified by reviewing AED-related adverse events reported to the FDA. Number of AEDs and AED accessories subject to FDA recall or safety alert between January 1996 and December 2005; annual AED advisory rates; and number of confirmed fatal AED-related device malfunctions reported to the FDA. During 2.78 million AED device-years of observation, 52 advisories (median [25th and 75th percentiles], 4.5 [3.0 and 5.0] per year) affecting 385,922 AEDs and AED accessories were issued. The mean (SE) annual number of AEDs affected by advisories was 5.1 (1.5) devices per 100 AED device-years. Overall, 21.2% of AEDs distributed during the study period were recalled, most often because of electrical or software problems. The AED advisory rate did not significantly increase during the study period, although the annual number of AED advisories (P for trend =.02) and AED advisory devices (P for trend = .01) did increase. Confirmed fatal AED-related device malfunctions occurred in 370 patients. Automated external defibrillators and AED accessory advisories occur frequently and affect many devices. Actual AED malfunctions do occur occasionally, although the number of observed malfunctions is small compared with the number of lives saved by these important devices. As the prevalence of AEDs continues to increase, the number of devices affected by advisories can also be expected to increase. Efforts should be directed at developing a reliable system to locate and repair potentially defective devices in a timely fashion.