161 children followed up postoperatively following splenectomy, 29% had spherocytosis, 14% Hodgkin's disease, 12% traumatic rupture of the spleen, 11% portal hypertension and 7% idiopathic thrombocytopenia. Postoperatively a slight wound infection occurred in 5% of the children, while complications were seen in 2% which could be interpreted as directly caused by the operation; in 23 patients, however, (i.e. 15%), severely infections occurred such as pneumonia, meningitis and sepsis. The lethality rate of the infected children was 31.8%. Postoperatively we determined the leucocyte count, thrombocytes and erythrocyte count, the immunoglobulins IgG, IgA, IgM and IgE, the serum concentrations of the complement components C3, C4 and the serum proteins alpha 1-antitrypsin and transferrin. The data obtained were compared with the corresponding data reported in the literature.