Using NEISS-AIP, we calculated an estimated 5946 (95% confidence interval [CI]04194Á7698) ED visits for sports-and recreation-related heat illnesses occurred annually from 2001 to 2009. Incidence was highest among males (72.5%) and among persons aged 15Á19 years (35.6%) and occurred most commonly during football (24.7%) and exercise (20.4%). Using RIO TM , we calculated an estimated 9237 (95% CI 08357Á10,116) heat illnesses resulting in time lost from participation occurred during high school sports annually from 2005 to 2009, most commonly during football (70.7%).