The nature of the relationship between inherited abnormalities of the clotting system and the occurrence of cerebrovascular accidents in young subjects is controversial. To evaluate the risk of cerebrovascular disease associated with such abnormalities, we analyzed a series of 23 consecutive patients in a case-control study with ischemic stroke proven by computerised tomography and aged below 45 years at admission, and a control group of 115 age- and sex-matched controls from the general population. No differences in antithrombin, protein C, protein S, heparin cofactor II, plasminogen or response to activated protein C were observed between cases and controls. None of the patients had a history of personal or familial thrombosis, and none had a reduction in the considered clotting factor below the reference range. We conclude that abnormalities of the clotting system are not associated with the occurrence of cerebrovascular abnormalities in the young and that routine screening for inherited thrombophilia is not appropriate in young patients with cerebrovascular disease.