Exertional heat stroke (EHS) during or following a marathon race can be fatal if not promptly recognised and treated. EHS is a true medical emergency and immediate cooling markedly improves the outcomes. It is critical to recognise EHS and stop the cell damage before the cascade of heat-induced tissue changes becomes irreversible. The goal is to keep the area that is >40.5° C under the body temperature versus time curve at <60 degree-minutes. Measuring the rectal temperature is the only precise estimate of core temperature available for field use. The field treatment of EHS is immediate, total-body cooling with ice-water tub immersion or rapidly rotating ice-water towels to the trunk, extremities and head, combined with ice packing of the neck, axillae and groin. Any combination of delayed recognition or cooling increases the potential for morbidity and mortality. For optimal outcomes, it is best to treat immediately with on-site whole-body cooling if cardiorespiratory status is 'stable' and then to transfer the runner for additional evaluation and care.