Patients with high hemoglobin need investigations to differentiate true from apparent erythrocytosis. Those with true erythrocytosis, deserve further work-up to differentiate polycythemia vera from secondary erythrocytosis. The diagnostic criteria for polycythemia vera are complex. Recently an activating point mutation in the JAK2 gene (JAK2-V617F) has been detected in majority of PV patients, but is not specific, and needs more evaluation. Patients may present with plethora, thrombosis in arterial or venous circulations, erythromelalgia, pruritis, hemorrhage, splenomegaly, gout, leukocytosis or thrombocytosis. Patients with polycythemia vera have significant morbidity and mortality due to thrombosis and hemorrhage. All patients deserve cytoreduction to hematocrit of 0.45 or less, preferably by venesection. Low dose aspirin (75 mg/day) is a universal recommendation, unless contraindicated. Those with high-risk disease or a progressive disease deserve cytoreduction using hydroxyurea or interferon alpha. Anagrelide may be used for thrombocytosis. With appropriate therapy, survival has improved from an average of 2 years to more than 10 years.