Background: Because sudden cardiac death increases with age, implantable cardioverter-defibrillators (ICDs) might greatly benefit the elderly. However, elderly patients are underrepresented in clinical trials, and comorbid conditions may attenuate benefit. Objective: The purpose of this study was to examine ICD prescription in the elderly. Methods: The ages, indications, and implanted ICD type of patients enrolled in the Advancements in ICD Therapy (ACT) Registry were compared to those from the National Cardiovascular Data Registry (NCDR). Results: The ACT Registry included 4,566 patients who underwent first ICD or cardiac resynchronization therapy ICD (CRT-D) implantation. Among these patients, 2.6% were 18-39 years old, 8.6% were 40-49 years, 20.1% were 50-59 years, 27.6% were 60-69 years, 29.0% were 70-79 years, and 12.0% were ≥80 years. In the six age groups, 82.5%, 79.4%, 77.3%, 80.1%, 77.7%, and 74.6% received devices for primary prevention, and single-chamber ICDs were implanted in 41.4%, 42.8%, 38.7%, 33.8%, 25.2%, and 28.1%, respectively (P <.0001). Two-year mortality rates increased incrementally from 5.80% to 17.80% in the six groups (P <.05). Noncardiac death was more common in older than in younger patients. Among patients ≥80 years old receiving a CRT-D, 78% had QRS duration and New York Heart Association class that met accepted implantation criteria. Age distribution, indication, and type of device were similar in the ACT Registry and in 74,476 patients in the NCDR. Conclusion: More than 40% of new ICDs and CRT-Ds are implanted in patients >70 years old and more than 10% in patients ≥80 years old. A significant proportion of those receiving a CRT-D did not fulfill accepted criteria for implantation. Noncardiac death occurred more frequently in older patients, but cardiac death rates were similar. © 2009 Heart Rhythm Society.