Thalassemia is a heterogeneous group of inherited disorders. The genetic defect results in reduced rate of synthesis of one of the globin chains that make up hemoglobin. Reduced synthesis of one of the globin chains causes the formation of abnormal hemoglobin molecules, and this in turn causes the anemia which is the symptom of the thalassemias. There are several forms of thalassemia. Thalassemias are classified according to which chain of the hemoglobin molecule is affected. The severity of the thalassemias is correlated with the number of affected globin loci: the greater the number of affected loci, the more severe will be the manifestations of the disease. Many of the thalassemia patients need splenectomy. The efficiency of splenectomy is not well studied. The research was conducted to study humoral and cellular immunity of 30 Thalassemia intermedia patients and 15 patients with Hemoglobin H disease in different periods after splenectomy. The functional activity of segmented neutrophil parameters before operation was low; in the second day and during a month after operation parameters gradually decreased; and in the remote terms after splenectomy. By first year after operation the same parameters have increased up to an initial level.