Platelet and F-VIII storage and phagocytic function of the spleen have been studied in 15 patients with β-thalassemia major who were not splenectomized and in 7 patients with Hb-S-β-thalassemia. Eight splenectomized patients, 4 had β-thalassemia major, and 11 healthy children served as controls. F-VIII elevation following adrenalin was not found to be sensitive index in the evaluation of “functional hyposplenia”. No functional derangement of the organ was shown in the patients with β-thalassemia major. However, at least 30 % of patients with Hb-S-β-thalassemia had functional hyposplenism with one of the tests. Higher platelet counts were observed in the latter patients, without palpable spleen, and the independence of the splenic functions were shown.