The clinical course of 16 patients with polycythemia vera (PV), treated in the period 1982 to 1993, was shown. Splenomegaly occurred in three fourths of these patients (75%), and hypertension was a major symptom. Thrombosis such as myocardial infarction and cerebral infarction was noted. Eight patients was treated with myelosuppressive agents and the 8 other patients were treated with phlebotomy. A 70-year-old male who was treated with mitobronitol (DBM) developed acute myeloblastic leukemia (AML) 11 years later. He was treated with multi-combination chemotherapy (BHAC-DMP), and entered complete remission, followed by early relapse. He became refractory to chemotherapy and died of acute pneumonia 6 months later. Median survival of 16 cases of PV was more than 10 years, and long-term treatment and care are necessary.