INTRODUCTION: Hematological diseases are seldom found as the etiology of ischemic strokes, but are frequently investigated by expensive laboratory tests after 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 ischemic 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 hematological pathology: polycythemia vera (4), secondary polycythemia (4), essential thrombocytemia (2), secondary thrombocytosis (4), multiple myeloma (1), CIVD (1), protein S deficiency (1), antiphospholipid antibody syndrome (4), moderate homocysteinemia (1). A literature review was undertaken for each hemopathy. CONCLUSION: In light of the results of these data, we concluded that a complete blood count provides sufficient hematological screening for the majority of patients hospitalized 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 history. Inherited thrombophilias are not a significant risk factor for arterial cerebral infarction and their investigation is only warranted for a sub-group of young patients with a cryptogenic stroke, in which group the prevalence is slightly increased. Moderate homocysteinemia must be considered as a cerebrovascular risk factor of minor importance, but potentially treatable by a substitution of vitamin B12, B6 and folates. The efficacy of this substitution in the prevention of cardiovascular events needs yet to be demonstrated.