The project was designed to test the assumption that certain psychosocial characteristics of occupational groups are associated with elevated myocardial infarction risk. All cases of myocardial infarction below the age of 65 in men living in the region of greater Stockholm during the years 1974-1976 were identified (deaths as well as survivals) in the official registries of hospitalizations and deaths. For each case two controls without infarction (in younger ages four) matched for age, area of residence and sex were selected randomly from the parish registries. For each case and control (n = 334 and 882, respectively) information was available regarding occupation. The psychosocial characteristics of each one of the 118 occupations were recorded by means of a nation wide interview survey (3876 working men) in 1977. Relative age-adjusted risks of developing a myocardial infarction were calculated for occupations in which many vs occupations in which few subjects reported a given characteristic (50% with most vs 50% with least). Shift work and monotony were associated with significant excess risk. Hectic work was not associated with excess risk by itself but in combination with variables associated with low decision latitude and/or few possibilities for growth it was associated with significant excess risk.