الفهرس 
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Abstract
Thalassaemia major is a hereditary anaemia caused by an abnormality of haemoglobin synthesis associated with ineffective erythropoiesis and rapid destruction of erythrocytes which if untreated leads to heart failure and death in early childhood (William et al,, 1990).
The presence of a-chain inclusions in the red cells of Bthalasaemic is the main cause of their shortened survival, but abnormalities of red cell metabolism may also play a role (Weatherall et al., 1989).These abnormalities which include lipid peroxidation of the membrane resulting from generation of superoxide and the formation of hemiehrome by the precipitated globin chains may be enhanced by vit. E deficiency and excess iron in the red cells (Rachmilewitz & Kahane, 1980).
The superoxide radical °2 is a frequently encountered intermediate of the reduction of dioxygen and it posses a threat to living cells much as does H202. Metaloenzymes, called superoxide dismutases,
SoDs, provide a defense against °2 and are found in virtually all
organisms. These enzymes properly called superoxide/superoxide ox id oreductases , catalyze the conversion of °2 to H202 + °2• (Fridovich, 1986).
This work is a comparative study to the level of superoxide dismutase in B-thalassaemic children and normal children aiming to show its role in prolongation of red cell life span and also, if there are some additional factors to increase its activity and hence affect also the red cell life.