Myocardial infarction is usually due to the acute formation of an occlusive thrombus within the coronary arteries, in most cases against a background of pre-existing coronary atherosclerosis. Both of these factors may be promoted by a procoagulant state of the hemostatic system. Plasma fibrinogen, factor VIIc, blood pressure, and lipid parameters were measured in 2,781 healthy men aged 40-65 in the Münster Heart Study (formerly known as the PROCAM Study). After 8 years of follow-up 130 coronary events (15 sudden cardiac deaths, 22 fatal myocardial infarctions, and 93 nonfatal myocardial infarctions) were observed. Plasma fibrinogen concentration and factor VIIc activity were significantly greater among men who suffered a coronary event. The mean plasma fibrinogen level of the event group exceeded that of the non-event group by 0.32 g/l [2.59 +/- 0.58 vs. 2.91 +/- 0.58 (mean +/- SD) respectively, P < 0.001]. The incidence of coronary events among men within the upper tertile of fibrinogen concentration was three times higher than among men within the lower tertile. Plasma factor VIIc activity was 112.4 +/- 20.1% in the event group and 108.7 +/- 21.4% in the non-event group (P < 0.05). Among men in the upper tertile of factor VIIc activity, the incidence of coronary events was 1.6 times that of men in the lower tertile. When fibrinogen and low density lipoprotein (LDL) concentration were considered together, there was a graded and dramatic eightfold increase in 8 year risk from 17 per 1,000 of population among men with both fibrinogen and LDL cholesterol in the lower tertiles to 130 per 1,000 in men with both of these parameters in the upper tertile. In men with LDL cholesterol in the lowest tertile, increasing fibrinogen levels did not increase the risk of a coronary event. The coagulation variables, fibrinogen concentration, and factor VIIc activity thus markedly improve our ability to predict coronary risk.