Sudden cardiac arrest (SCA) is the leading cause of death in exercising young athletes. Three factors--prompt recognition of SCA, the presence of a trained rescuer to initiate cardiopulmonary resuscitation (CPR) and access to early defibrillation through on-site automated external defibrillators (AEDs)--are critical to improving survival. Schools, clubs and organizations sponsoring athletic events should have an established emergency response plan for SCA. Essential elements of an emergency response plan include an effective communication system to alert first responders and retrieve the AED, training of anticipated responders in CPR and AED use, access to an AED for early defibrillation, integration of on-site AED programmes with the local emergency medical services system, and practice and review of the response plan. Timely access to AEDs at training and sporting competitions permits effective management of SCA and the prevention of sudden cardiac death in athletes. SCA should be suspected in any collapsed and unresponsive athlete and an AED applied as soon as possible for rhythm analysis and defibrillation if indicated. This article reviews emergency response planning for SCA and highlights recent data that provide a compelling case for the essential role of AEDs in the athletic setting.