Myeloproliferative disorders including polycythemia rubra vera (PRV), essential thrombocythemia, myelofibrosis and chronic myeloid leukemia, their etiology, genetic association, clinical manifestations, laboratory diagnosis and outline of treatment are described. Differences between primary (PRV), secondary and pseudopolycythemia are given in tabloid form. Differences between primary and secondary myelofibrosis are also discussed.