Introduction. Hematological diseases are seldom found as the etiology of isch emic strokes, but are frequently investigated by expensive laboratory tests afte r a first cerebral vascular event. Methods. In the Lausanne Stroke Registry, we retrospectively reviewed the cases of patients hospitalized between 1979 and 2001 for a first is chemic arterial stroke which was attributed to a hematological etiology. Of 4697 patients, 22 (0.47 per cent) had a stroke due to one of the following hematolog ical pathology: polycythemia vera (4), secondary polycythemia (4), essential thr ombocytemia (2), secondary thrombocytosis (4), multiple myeloma (1), CIVD (1), p rotein S deficiency (1), antiphospholipid antibody syndrome (4), moderate homocy steinemia (1). A literature review was undertaken for each hemopathy. Conclusion . In light of the results of these data, we concluded that a complete blood coun t provides sufficient hematological screening for the majority of patients hospi talized for an arterial stroke. The antiphospholipid antibody syndrome is a rare cause of cerebral infarction, which needs to be investigated in young patients, in cases of multiple or recurring stroke or in the presence of a typical histor y. Inherited thrombophilias are not a significant risk factor for arterial cereb ral infarction and their investigation is only warranted for a sub-group of yo ung patients with a cryptogenic stroke, in which group the prevalence is slightl y increased. Moderate homocysteinemia must be considered as a cerebrovascular ri sk factor of minor importance, but potentially treatable by a substitution of vi tamin B 12, B 6 and folates. The efficacy of this substitution in the prevention of cardiovascular events needs vet to be demonstrated. Introduction. Hematological diseases are seldom found as the etiology of isch emic strokes, but are frequently investigated by expensive laboratory tests afte ra first cerebral vascular event. Methods. In the Lausanne Stroke Registry, we retrospectively reviewed the cases of patients hospitalized between 1979 and 2001 Of 4697 patients, 22 (0.47 per cent) had a stroke due to one of the following hematological pathology: polycythemia vera (4), secondary polycythemia (4), essential thr ombocytemia (2), secondary thrombocytosis (4), multiple myeloma (1), CIVD (1), p rotein S deficiency (1), antiphospholipid antibody syndrome undertaken for each hemopathy. Conclusion. In light of the results of these data, we said that a complete blood coun t provides sufficient hematological screening for the majority of patients hospi talized for an ar The antiphospholipid antibody syndrome is a rare cause of cerebral infarction, which needs to be investigated in young patients, in cases of multiple or recurring stroke or in the presence of a typical histor y. Inherited thrombophilias are not a significant risk factor for arterial cerebral ral infarction and their investigation is only warranted for a sub-group of yo ung patients with a cryptogenic stroke, in which group the prevalence is slightl y increased. Moderate homocysteinemia be be considered as a cerebrovascular ri sk factor of minor importance, but potentially treatable by a substitution of vi tamin B 12, B 6 and folates. The efficacy of this substitution in the prevention of cardiovascular events needs vet to be demonstrated.