The increase in cardiovascular risk associated with having non-insulin-dependent diabetes mellitus (NIDDM) is far greater in women than men. Conventional risk factors do not account for this excess, and attention has focused on the possible contribution of abnormalities of fibrinolysis and coagulation in NIDDM. In the general population a number of hemostatic factors have been shown to predict the occurrence or progression of coronary artery disease. To investigate sex differences in coagulation and fibrinolysis in NIDDM, we measured levels of fibrinogen, factor VII:C, von Willebrand factor, plasminogen activator inhibitor-1, and tissue plasminogen activator in 213 NIDDM subjects (124 men and 89 women) who were not receiving insulin therapy. The women had higher levels of factor VII:C (144% versus 120.5% in men, P < .0005) and plasminogen activator inhibitor-1 activity (25.6 versus 17.0 U/mL), and these differences remained significant when account was taken of the higher body mass index (29.6 versus 28.0 kg/m2, P = .02), glycosylated hemoglobin (7.2% versus 6.8%, P < .05), and cholesterol levels (6.3 versus 5.7 mmol/L, P < .0005) in women than men. In contrast, levels of fibrinogen (3.2 versus 3.1 g/L), tissue plasminogen activator antigen (10.6 versus 11.2 ng/mL), and von Willebrand factor (1.27 versus 1.23 IU/mL) were no different between women and men, respectively. These results suggest that elevated levels of plasminogen activator inhibitor-1 and factor VII:C may contribute to the increased cardiovascular risk of NIDDM that is particularly marked in women.