National injury surveillance systems provide a unique opportunity to examine heat illness in sports and recreational settings. NEISS-AIP and High School RIO TM demonstrate different approaches to studying this problem. Results from both analyses indicate that heat illness causes substantial morbidity among sports and recreation participants. We need to find new ways to target effective heat illness prevention messages to those at greatest risk to reduce morbidity and prevent mortality. Continued surveillance is also warranted to monitor trends and evaluate interventional activities.