Essential thrombocythemia (ET) is a myeloproliferative neoplastic disease characterized by abnormal proliferation of megakaryocytes in the bone marrow leading to elevated platelet counts in the peripheral blood. In the present study, we aim to assess the long-term complications of ET and its treatments in terms of the development of secondary malignancies, bone marrow fibrosis and leukemic transformation. One hundred and twenty four patients with ET were included into the study. Retrospective data were collected from our database of myeloproliferative disorders. There were 75 (60.5%) men and 49 (39.5%) women with a median age of 53 (range, 20-80) years. The data indicated that 3 patients treated with hydroxyurea (HU) had suffered of bladder cancer, non-small cell lung cancer and thyroid papillary cancer, 2 patients without treatment suffered of breast cancer and neuroendocrine cancer and 2 patients treated with combination (HU and anagrelide) suffered of acute myeloid leukemia (AML) and prostate cancer. In total, 16/124 patients (12.9%) developed bone marrow fibrosis. Nine of the patients (7.2%) who developed bone marrow fibrosis were receiving HU, 5 of them (4%) were using HU and anagrelide and 2 of them (1.6%) were followed without treatment (p= 0.44). The age (p= 0.03), hemoglobin level at diagnosis (p< 0.001), white blood cell level at diagnosis (p= 0.02), CRP level (p= 0.01), pre-treatment hemorrhage rate (p< 0.001) were statistically significant different between the patients who developed myelofibrosis and patients who did not develop myelofibrosis. The results of this study disclosed that there was no statistically significant difference regarding the development of bone marrow fibrosis, leukemic transformation or secondary malignancies with regard to the treatment options of ET. Moreover, ET patients who had received HU and anagrelide treatment has better OS than the other patient cohorts. Keywords: Essential thrombocythemia, Myelofibrosis, Secondary malignancy, Hydroxyurea, Acute myeloid leukemia.