We report a rare case of fulminant autoimmune hemolytic anemia (AIHA) with multiple organ failure (MOF). A 40-year-old man was emergently admitted to our hospital because of conscious disturbance and jaundice. The peripheral blood revealed RBC 68 x 10(4)/microliter, Hb 3.5 g/dl, Ht 8.9%, Ret 30% (20,400/microliter), WBC 20,300/microliter, Plts 16.9 x 10(4)/microliter, indirect bilirubin 9.4 mg/dl. Both direct and indirect Coombs test were positive and the IgG autoantibody was identified. Bone marrow aspiration revealed hypercellularity with increased megakaryocytes and erythroid hyperplasia. The patient was diagnosed as having idiopathic warm type of AIHA and the therapy was started with prednisolone 80 mg/day from the first day of admission but hemolysis with reticulocytopenia was so rapidly progressive that he was in acutely life-threatening state and MOF (acute renal failure, adult respiratory distress syndrome, congestive heart failure, liver dysfunction, rhabdomyolysis) appeared on the third hospital day. Plasma exchange therapy and hemodialysis were started and high dose methylprednisolone was given soon after rapid administration of sufficient blood transfusion. Dramatic improvement of hemolysis was noted and MOF was controlled after starting these therapies, but he died of exacerbation of MOF probably due to sepsis 40 days later.