This summer Europe has again been affected by a major heat wave and England triggered its heat wave response plan for the first time.1 In 2003, the impact of the heat wave in central France was unprecedented, with more than 14 000 excess deaths attributed to the 20 day event.2 This year, France has reported considerably fewer deaths, and the authorities can claim some credit for effective public health intervention. The United Kingdom experienced a more severe heat wave than in 2003, but the full impact on health is not yet known. Schools, offices, hospitals, and the transport infrastructure were all affected badly. Although much is known about the regulation of body temperature in healthy fit adults, little research has been undertaken on the social and environmental determinants of heat related mortality. People with psychiatric disorders, depression, cardiovascular and cerebrovascular conditions,3 and diabetes4 are at high risk of death during a heat wave. Specific drugs, such as …