1. Diagnosis or suspected diagnosis of PV, ET, or IMF. The World Health Organization Criteria will be used for diagnosing this disorder. In brief, the criteria for PV is hemoglobin greater than 18.5 g/dL in men and greater than 16.5 g/dL in women and splenomegaly on palpation in the absence of secondary erythrocytosis. If splenomegaly is absent, the patient must have 2 of the following 4 minor criteria: platelet count greater than 400 x 10(9)/L, leukocyte count greater than 12 x 10(9)/L, marrow biopsy with trilineage increase in cellularity, and low serum erythropoietin level. The criteria for EF is a platelet count greater than 600 x 10(9)/L with no known cause of reactive thrombocytosis and a normal hemoglobin. The criteria for IMF is fibrosis of the bone marrow and splenomegaly without preceding PV, ET or chronic myelogenous leukemia.