Fibrinogen is an important determinant of blood haemostasis and viscosity. Several prospective studies have demonstrated plasma fibrinogen concentration to be an important predictor of cardiovascular disease, both in healthy subjects and in patients with coronary disease. Subjects with high plasma fibrinogen concentrations have a two to four-fold increased risk of developing cardiovascular disease compared to those with low fibrinogen. Whether fibrinogen is a causative factor for atherosclerosis or a marker of the inflammatory process of atherosclerosis remains to be proven.