A 43-year-old woman who developed thrombotic thrombocytopenic purpura was treated successfully with high doses of prednisone and a splenectomy. Imprints from the cut surface of the spleen showed marked phagocytosis of all the cellular elements of the blood. This observation suggests that hypersplenism, in addition to vascular occlusion, may play a major role in the physiopathology of some cases of thrombotic thrombocytopenic purpura.