Alloimmunization to red blood cell antigens are frequent findings in Egyptian transfusion-dependent thalassemic patients. The aim of this work is to evaluate the presence of alloantibodies and autoantibodies in regularly transfused thalassemic patients, identifying its type & and to evaluate the different factors influencing the development of alloantibodies.We concluded that 28.45 % of patients developed alloantibodies majority of them were against the Kell and Rh blood group systems and1.1% of patients developed autoantibodies. We recommend that all thalassemia transfusion dependent patients be screened for antibody development before each transfusion. Also to take measures to reduce the possibility of alloantibody development.