Beta Thalassemia major patients receive repeated transfusions in order to compensate anemia and use desferal to remove iron overload. Comparing immunoglobulins and complement components in the serum of these patients with normal range shows a significant increase (P<0.001) in IgG, IgA and IgM and a decrease in C3c and C4. The regression analysis confirms a relation between the numbers of transfusions and the mentioned immunological factors that means increasing the number of transfusions, increases immunoglobulins and decreases the complement. Also, this evaluation shows that use of washed RBC and regular in take of desferal will prevent excessive increase of immunoglobulins or decrease of complement