In brief: It is generally recommended that rectal rather than oral temperature be used to diagnose heat injury in runners. However, because of lack of privacy after a race, oral temperature is often used. In this study oral and rectal temperatures of seven women and 16 men were taken simultaneously three minutes, 15 minutes, and 30 minutes after a race in a tropical climate. The mean rectal temperature at three minutes was an elevated 103.5 F, while the mean oral temperature was a normal 98 F. This study shows the importance of using rectal rather than oral temperature for accurate assessment and diagnosis of heat injury.