The aim of our study was to prove or disprove the independent prognostic importance of fibrinogen after myocardial infarction. Plasma fibrinogen levels were determined on admission in 135 patients with an acute myocardial infarction and symptoms up to 4 h (mean: 1.8 h) immediately before starting fibrinolytic treatment with 1.5 mio U. streptokinase i.v. All patients were free from other diseases which are known to cause elevated fibrinogen levels. Coronary angiography was carried out in 87%. During a mean follow-up period of 26.2 months 31 coronary events could be observed in 26 patients: 18 reinfarctions, 6 cases of sudden death, and 7 coronary artery bypass graft surgeries because of new symptoms. While plasma fibrinogen levels were higher in smokers than in non-smokers (3.30 vs 2.94 g/l p = 0.011) and correlated with the number of involved coronary arteries (p = 0.08), values were similar in patients with and without coronary events during follow-up (3.07 vs 3.16 g/l, p = 0.70). This applied as well to univariate analysis as to multivariate Cox's regression model. We conclude that plasma fibrinogen levels determined very early in patients with acute myocardial infarction do correlate with other important prognostic variables, but have no independent prognostic importance.