This article provides an overview of recently accumulated evidence on the pathogenetic role of fibrinogen in various vascular beds; and tries to elucidate determinants for patients' susceptibility so that subgroups at particular risk of severe clinical complications can be characterized more accurately. Based on the considerably elevated risk of cardiovascular complications associated with increased levels of plasma fibrinogen, the potential value of lowering fibrinogen in the primary or secondary prevention of atherosclerotic disease is now recognized as an important topic for consideration. Recent progress in this field will also be reviewed.