IGF-1R expression was measured by flow cytometry in 19 patients with essential thrombocythemia (ET), 28 myelofibrosis (MF) patients including 5 post-ET-MF, 5 post-PV-MF, and 18 primary myelofibrosis (PMF). The patients who were treated with hydroxyurea and ruxolitinib were excluded. The results showed that ET and MF patients had significantly elevated IGF-1R levels compared with controls; ET (183.0, 86.8–327.0) (n = 19) and MF (135.1, 73.01–247.6) (n = 28) patients had significantly elevated IGF-1R levels compared with controls (47.75, 34.50–68.79) (n = 30) (P<0.05). PV patients had elevated levels compared with ET and MF patients, while no significant difference was found between ET and MF patients.