Marmot M G (London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK). Alcohol and coronary heart disease. International Journal of Epidemiology 1984; 13: 160–167. The data on two questions are reviewed: does heavy alcohol intake increase the risk of coronary heart disease (CHD)? And, is moderate intake protective? Identified alcoholics and problem drinkers have an increased risk of CHD, and in Britain there is a correlation among 22 towns, between the proportion of heavy drinkers in a town and CHD mortality. Of seven longitudinal studies reviewed, one shows heavy drinkers to have an increased CHD incidence. An inverse association between alcohol consumption and CHD mortality is seen in international comparisons and in time trends in the USA. Of six case-control studies reviewed from England and the USA, all show an inverse association between CHD and alcohol consumption which persists after control for other risk factors. Longitudinal studies, in Japanese-Americans, white American men and women, British civil servants, Puerto Ricans, Yugoslavs and Australians, all show moderate drinkers to have a lower CHD risk than abstainers. Abstainers are likely to differ from moderate drinkers in a number of ways. To date it has not proved possible to show that any of these differences account for the higher CHD risk of abstainers. The apparent protective effect is not large (RR = 0. 5) but the consistency of the association and the existence of plausible mechanisms increase the likelihood that the negative association is causal. However, if alcohol intake were to increase in the population the social and medical consequences would be large. An increased intake is therefore not recommended as a community measure for CHD prevention.