Vesicles are part of the red blood cells membrane which can be found in a small number in normal apoptotic process and increased in some diseases. In the present study, the authors measured the percentage of red blood cell vesicles in healthy subjects (n = 7), patients with alpha-thalassemia or Hemoglobin (Hb) H disease (n = 7), beta-thal/Hb E with nonsplenectomized (n = 5) and splenectomized (n = 7) before and after induction heated at 48.6 degrees C by using flow cytometry. It was found that the percentage of vesicles in every group were not statistically significantly different (p > 0.05) between pre and post incubation at 5 min. The percentage of vesicles of healthy subjects, beta-thal/Hb E nonsplenectomized patients and splenectomized patients were highest when induced by heating for 60 min. For patients with Hb H disease, the percentage of vesicles was maximum at 30 min when compared with healthy subjects, beta-thal/Hb E nonsplenectomized patients and splenectomized patients, respectively. In the present study, the authors report the significant increase of the percentage of vesicles in Hb H disease, beta-thal/Hb E nonsplenectomized and splenectomized after induction by heat when compared with healthy subjects. These findings may support the different pathology of the red blood cells found in alpha- and beta-thalassemia.