THE TERMINATION of polycythemia vera in acute leukemia is an infrequent occurrence. Because of the scarcity of such reports opportunity is taken to report one such case and to review others noted in the previous literature. T. K., a 65-year-old white woman, was admitted to the Albert Einstein Medical Center, Southern Division, on March 20, 1953, because of weakness and pallor. She was known to have polycythemia vera since June, 1941, and was treated with venesections, x-rays, and P32 (Table). Physical examination revealed an elderly woman in acute distress. B. P., 130/70; pulse, 100; respiration rate, 20; temperature, 102 F. Marked pallor, purpura, and splenomegaly were noted. There was no icterus, adenopathy, hepatomegaly, or glossitis. Blood studies showed RBC, 3,340,000; Hb., 9.7 gm.; reticulocytes, 0.9%; platelets, 140,000; WBC, 7400, with 1% segmented cells, 5% lymphocytes, 3% myelocytes, 3% promyelocytes, and 88% blast forms. A sternal marrow biopsy revealed a