Implantable cardioverter defibrillators have become one of the preferred methods for treating many life- threatening ventricular arrhythmias. Many tens of thou sands of these devices have been implanted and this, together with the ease of worldwide travel, has made it more likely that anesthesiologists everywhere may come into contact with these patients either for elective or emergency surgery. These patients present unique anesthetic challenges because of the combination of the device and severe underlying cardiac disease. This article presents an overview of the implantable defibril lator as it affects the anesthesiologist, including device function, device assessment, electromagnetic interfer ence, and perioperative management.