Mossbauer spectroscopy was used to monitor, over a period of three days, the form of iron in iron-loaded spleen tissue following splenectomy from a patient with beta-thalassemia. The tissue was stored at room temperature for a three day period in order to allow degradation and autolytic processes to take place. The majority of the iron in the fresh spleen tissue was found to be in the form of inorganic polynuclear iron(III) oxyhydroxide clusters associated with ferritin and hemosiderin. After three days, some of the iron had been reduced to high-spin iron(II). (C) 1998 Elsevier Science S.A.