A sample of in all 119 young adults below the age of 55, with ischemic cerebrovascular disease (TIA and minor stroke), was investigated later than three months after acute disease. Factor VIII biological activity and antithrombin antigen were significantly (p less than 0.001) increased as compared to 80 healthy controls. In combination, these two variables correctly classified 85 percent of patients and controls at a stepwise discriminant analysis. Factor VIII related antigen was increased (p less than 0.02) in patients with atherosclerotic signs at cerebral angiography and in postmenopausal female patients (p less than 0.001). It is suggested that high levels of factor VIII might predispose for thrombosis/atherosclerosis. Antithrombin biological activity was normal in spite of high antithrombin antigen levels, possibly indicating a relative insufficiency in the antithrombin defense line. It is concluded that young stroke patients provide good opportunities to look for early operating factors and predictors in human atherosclerosis and arterial thromboembolism.