One hundred and fifteen beta thalassemia major outpatients attending the Thalassemia Center Department of Child Health, Medical School University of Indonesia Dr. Cipto Mangunkusumo General Hospital for routine blood transfusion and hematology examination, participated in this study. There was a negative correlation between the size of the spleen and the peripheral blood parameters. All peripheral blood parameters tend to decrease with the enlargement of the spleen, and the condition is reversed after splenectomy. We observed that hypersplenism starts when the spleen is as big as S (V – VI). The hemoglobin electrophoresis pattern from beta thalassemia major patients receiving repeated blood transfusion did not show a dense HbF fraction, 90 ...