Peripheral blood cytopenia due to documented marrow necrosis is an unusual occurrence. This report describes a diabetic patient who presented with profound anemia and thrombocytopenia. Extensive bone marrow necrosis was demonstrated. He had a large renal cyst that contained hyphae later identified as Mucor species. It is postulated that the marrow necrosis was a direct or indirect result of Mucor infection. The phenomenon of bone marrow necrosis in reviewed.