Polycythemia vera (PV) is a blood disorder in which the first expression may be an ischemic stroke. Stroke mechanism in PV is usually attributed to a hyperco-agulability state and blood stasis. We report a case of a patient with PV presenting with recurrent ischemic stroke associated with the development of large intracranial stenosis in a period of 1 month. Stenosis was associated with microembolic signals detected by transcranial Doppler. One year later and after hematocrit control, stenosis persisted but microembolic signals disappeared. We discuss similar reports in the literature and the possible pathophysiological mechanism of large-vessel damage in these patients.