Thromboses and phenotypic evolutions (leukemia, myelofibrosis) are the most frequent complications in Polycythemia vera (PV) and essential thrombocythemia (ET). Aquagenic pruritus (AP) is not only PV symptom, but is also present in ET. The presence of pruritus in PV is associated with a lower risk of arterial thrombosis. Among 396 ET patients, presence of AP characterizes patients with higher risk of morbidity: more proliferative, more symptomatic at diagnosis and higher risk of thromboses and evolutions. The systematic determination of the presence of AP in ET patients should permit to better identify these high-risk patients for better management and follow-up. This article is protected by copyright. All rights reserved.