Polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF), collectively known as Philadelphia-negative (Ph-negative) chronic myeloproliferative neoplasms (MPNs), MPNs represent the most common causes of splanchnic vein thrombosis (SVT), including Budd-Chiari syndrome (BCS) and portal vein thrombosis (PVT). The JAK2V617F mutation has been demonstrated in most of the Ph-negative chronic MPNs. The study objective was to assess the diagnostic value of JAK2V617F mutation in patients with SVT in a group of 68 patients with SVT (42 PVT,19 BCS, 7 combined PVT and BCS). By DNA-melting curve analysis, the JAK2V617F mutation was detected in 42.1 % of BCS, 38.1 % of PVT and 71.4 % of combined PVT and BCS groups. Thirteen of 15 (86.6 %) SVT patients with overt MPN and 16 of 53 (30.1 %) SVT patients without overt MPN (patients with either normal blood counts or cytopenias), including 6 of 16 with BCS (37.5 %), 7 of 33 with PVT (21.2 %) and 3 of 4 with combined BCS and PVT (75 %) possessed JAK2V617F mutation. A substantial proportion of patients with SVT were recognized as carriers of the JAK2V617F mutation despite the absence of overt signs of MPN. Receiver Operating Characteristic (ROC) curve analysis determined a platelet count of 190,000 mm(3) (area under the curve; AUC = 0.724, p = 0.002) and a white blood cell (WBC) count of 8,150 mm(3) (AUC = 0.76, p = 0.001) as the best cut-off values for the highest sensitivity and specificity ratios of the JAK2V617F mutation in patients with SVT. A significant positive correlation existed between the JAK2V617F mutational status of SVT patients and the WBC and platelet counts. Our results imply that JAK2V617F mutation screening should be an initial test for MPN in patients with SVT.