A review of the literature suggests that the geographical and social class distribution of ischaemic heart disease (IHD) could be partly explained by variations in degrees of cold exposure, which includes wind and rain as well as temperature, with frequent exposure to cold being more harmful than steady exposure. Blood pressure (BP) and serum cholesterol are raised in response to acute and chronic exposure to cold. Smoking and cold produce similar physiological changes which increase the risk of IHD, while regular exercise blunts the physiological effects of cold and other stresses. There are many acute responses to cold which could trigger a myocardial infarction (MI) and therefore cold is probably a major precipitating factor in many cases of MI. Public health measures to improve domestic housing and the working environment may produce a significant impact on the incidence of IHD.