In a prospective, randomized trial, patients with polycythemia vera who had a hematocrit target of less than 45% had a significantly lower rate of cardiovascular death and major thrombosis than did those with a hematocrit target of 45 to 50%. Polycythemia vera is a rare hematologic neoplasm characterized by clonal proliferation of multipotent bone marrow progenitors, leading to abnormal production of erythroid cells and an increased red-cell mass. 1 – 4 Acquired mutations in JAK2 ( JAK2 V617F and exon 12 mutations) are found in almost all patients with polycythemia vera. 5 , 6 Major causes of death and complications include thrombosis, bleeding, and hematologic transformation into overt myelofibrosis or acute leukemia. Recommendations for the management of polycythemia vera are based on thrombotic risk and a limited number of randomized clinical trials and observational studies that described the clinical course of the disease and . . .