Forty-six patients who were diagnosed with JAK2 V617F-unmutated chronic myeloproliferative Bcr-Abl-negative disease between March 2004 and January 2013 were included in this study; 73.9% (n: 34) of all patients had ET and 26.1% (n: 12) had PMF. The gene discussed is JAK2; the disease is essential thrombocythemia.