Exertional heat stroke usually occurs in warm climates. Increased serum levels of liver enzymes is a common finding in this condition, whereas liver failure is a more rare event that carries a poor prognosis. Liver transplantation has been recommended as treatment in cases of severe liver failure, but no long-term survival after this procedure in exertional heat stroke has been described. We report the case of a 31-year-old man who had a heat stroke after running 5 km at 21 degrees C. He developed severe liver damage, with serum alanine aminotransferase (ALAT) activities increasing to 16,410 U/l (reference values, 10-50 U/l) after 48 h, concomitantly with a pronounced coagulation disturbance, with Normotest (NT) decreasing to 12% (international normalized ratio (INR) = 4.2) (reference values, 70%-130% for NT and 0.8-1.2 for INR). A liver biopsy on the 5th day after the incident showed extensive liver cell necrosis. The patient was referred to be considered for liver transplantation but recovered completely on conservative treatment. We conclude that exertional heat stroke is a diagnostic possibility also in temperate climates and that severe liver failure may ensue. The liver injury is reversible, and the indications for liver transplantation in this situation have not been clarified.