Background: Portal vein tumor thrombosis (PVTT) is a serious complication and a major metastatic way of HCC; although it has been suggested that portal vein thrombosis (PVT) associated with untreated HCC are almost always malignant, still benign portal vein thrombus should be considered as well.Aim of the work: The aim of this study was to assess the value of ultrasound-guided fine needle aspiration in the differential diagnosis of portal vein thrombosis associated with hepatocellular carcinoma.Patients and methods: This study included 20 patients with chronic liver disease and hepatocellular carcinoma (associated with portal vein thrombosis). All the patients underwent color coded duplex sonography and ultrasound-guided fine-needle aspiration cytology of portal vein thrombosis.Results: -FNAC was positive for malignancy in 14/20 cases (70%).-Comparing the cytology results with the Doppler sonographic findings we demonstrated that the presence of either complete thrombus and/or positive intralesional signals were exclusive for malignant nature (P-value was 0.042 and 0.002 respectively), color coded duplex sonography had a sensitivity of 78.6%, specificity of 100%, positive predictive value of 100%, negative predictive value of 66.7% with a total accuracy of 85% for diagnosis of malignancy.Conclusion: Ultrasound-guided fine-needle aspiration of portal vein thrombosis is a safe, feasible, well –tolerated procedure with a high diagnostic value .