A greater life expectancy has led to an increasing proportion of elderly patients. Increasing age is an important risk factor for cardiovascular disease, but the mechanism of risk is not well understood. Because thrombosis plays a key role in plaque development and the onset of acute coronary syndromes, the age-related increase in cardiovascular risk may be a result of a prothrombotic imbalance. The study aim was to examine the relation between age and thrombotic potential in the Framingham Offspring Cohort. Hemostatic factors previously associated with cardiovascular risk were measured in 3,230 patients (55% women) without evidence of cardiovascular disease who were participating in cycle 5 of the Framingham Offspring Study. The subjects were divided by age into decades. Advancing age was associated with a significant increase in fibrinogen and von Willebrand factor levels and measures of impaired fibrinolytic potential (plasminogen activator inhibitor and tissue plasminogen activator antigens). For men, the mean fibrinogen levels were 21% higher in those > or =70 years versus those aged <40 years (326 vs 268 mg/dl, p <0.001 for linear trend). The mean fibrinogen levels were 15% higher in older than in younger women (330 vs 286 mg/dl, p <0.001). The significant relations persisted after multivariate adjustment. In conclusion, advancing age is associated with elevated levels of hemostatic factors indicative of a prothrombotic state. Because these factors are also associated with endothelial dysfunction, these findings are consistent with an injurious effect of age on the endothelium. Measures to reduce thrombotic potential may be of particular value in the elderly, because they counter the prothrombotic state that develops with aging.