In a prospective population study of middle aged women socioeconomic factors and physical activity as initially reported were related to the 12 year incidence of ischaemic heart disease and to total mortality. There was a significant age specific correlation between low socioeconomic status according to the husband's occupation and myocardial infarction. No such association was seen between the socioeconomic status of the women themselves and myocardial infarction. Women with a low educational level had a significantly increased age specific incidence of angina pectoris. There was no significant correlation between marital status or number of children and incidence of ischaemic heart disease or overall mortality. Women who initially reported low physical activity at work during the last year had a significantly increased age specific 12 year incidence of stroke and death, as did those who reported low physical activity during leisure hours in whom the incidence of myocardial infarction and electrocardiographic changes indicating ischaemic heart disease were also increased. Multivariate analyses showed that the association between low educational level and incidence of angina pectoris was independent of socioeconomic group, smoking habits, systolic blood pressure, indices of obesity, serum triglycerides, and serum cholesterol. Similarly, low physical activity during leisure hours seemed to be an independent risk factor for stroke, and low physical activity at work was an independent risk factor for overall mortality.