A 33-year-old man with heat exhaustion was admitted to our hospital suffering from severe chest pain. Serum creatine kinase elevation and new Q waves revealed myocardial infarction of the inferior wall. Technetium-99m-pyrophosphate suggested diffuse myocardial damage, although the left ventricular function was normal by echocardiography. This case highlights the importance of early recognition of heat stroke and heat exhaustion, as they are associated with widespread tissue injury.