Four clusters of psychosocial risk factors for coronary heart disease (CHD) are reviewed. Socio-economic disadvantage acts through a number of influences to increase CHD risk. In advanced industrialized nations those in the lower social strata now have much higher CHD risk than persons in middle and upper social classes. Sustained disturbing emotions represent a second cluster. Anxiety, depression and other indices of neuroticism have frequently been found in association with angina pectoris and cardiac death, though not with myocardial infarction (MI). However, sleep disturbances are associated with angina, cardiac death and MI. The Type A behaviour pattern results from an interaction between a self-activating individual and an environment which rewards hurried and competitive activity. Despite a small number of negative findings, the Type A pattern has been shown in cross-sectional, retrospective and prospective studies by many research teams to be associated with a variety of manifestations of CHD. A fourth, and more recently recognized cluster of psychosocial risk factors, may be grouped together under the general heading of "overload". Many investigations have now shown, for example, that excessive workload is a powerful predictor of CHD risk. It is suggested that all four clusters share the common property of exposing the individual, either chronically, or in frequently recurring episodes, to excessive psychological demands. They appear to exert their pathogenic influence through long-term mechanisms such as atherosclerosis or plaque formation, rather than by precipitating sudden coronary events.