In the 'Prospective Cardiovascular Münster' (PROCAM) study since 1979 employees have been examined for cardiovascular risk factors and held under observation for the onset of clinically significant signs of atherosclerosis (myocardial infarction, stroke, coronary death). Until the end of recruitment (end of 1985) 20,060 male and female employees aged 17-65 from 52 industrial companies in Westfalia have participated. The voluntary examination at the start of the observation period includes a standardised questionnaire, a physical examination, blood pressure measurements and an ECG. Blood samples are taken after an overnight fast. The data presented here describe the longitudinal evaluation of initially healthy men aged 40 to 65 who had suffered no myocardial infarction or stroke before the examination. In an uniform follow-up period of four years 73 myocardial infarctions and coronary deaths were observed while 2681 men had survived without myocardial infarction or stroke. By far the best single parameter for establishing a risk group was HDL cholesterol. Using the characteristic hyper/dyslipoproteinemia which means cholesterol greater than = 300 mg/dl or HDL cholesterol less than 35 mg/dl combined with cholesterol greater than = 200 mg/dl and/or triglyceride greater than = 200 mg/dl or a multiple logistic function including age, cholesterol, HDL cholesterol, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris and a family history of myocardial infarction patients at high risk for coronary heart disease could be identified. More than two thirds of new events happened in each of these high risk subgroups, which comprise less than 20 percent of men under consideration each.