Thalassemia is a hereditary hemolytic anemia caused by mutations in the globin gene complex. Circulatory disturbances, including arterial and venous thrombosis, have been observed in these patients. Aggregability of abnormal RBC and the high level of membrane-derived microparticles, stemming from activated platelets and other blood cells, have been shown to enhance procoagulant activity. It is also thought that RBC membrane-derived vesicles contribute to defects in coagulation.The present work aimed to determine the percentage of RBCs vesicles in the peripheral blood of β-thalassemic patients, using flow cytometry, and study its relationship to the degree of severity of anaemia.Thirty-one β-thalassemic patients and 23, age and sex matched healthy controls were included in this study. Estimation of RBCs vesicles percentage, by flow cytometry, was done to all patients and controls.The RBCs vesicles were present in both normal and thalassemic blood samples; but their percentage was significantly higher in the β-thalassemia group as compared with the control group.The percentage of circulating RBCs vesicles was significantly higher in splenectomized thalassemic patients as compared with non splenectomized cases and with controls.No correlation was found between RBCs vesicles percentage and clinical or haematological data of β-thalassemia patients.It was concluded that flow cytometric determination of RBCs vesicles percentage is simple, reliable and may offer new insights in the assessment of possible thrombotic complications in patients with thalassemia.