A 26-year-old man was referred to our hospital with vomiting and high fever. He was disoriented and laboratory results showed microangiopathic hemolytic anemia (Hb 7.1 g/dl) and severe thrombocytopenia (15 x 10(3)/microl). The diagnosis of thrombotic thrombocytopenic purpura (TTP) was established. The activity of von Willebrand cleaving protease (ADAMTS13) was found to be remarkably low (<0.5%) and the high activity of the inhibitor (11.0 Bethesda U/ml) was detected, confirming the diagnosis of typical acquired TIP. Although he had been successfully treated with daily plasma exchange and methylprednisolone, he relapsed after a week. To this therapeutic strategy we added four weekly doses of rituximab (375 mg/m2) and two weekly doses of vincristine (1 mg/m2) simultaneously. The response was very rapid and complete, that is, the platelet count recovered to normal seven days after the first rituximab and vincristine treatment. The patient maintains complete remission nine months later under the administration of 17.5 mg prednisolone. Recovery of the plasma ADAMTS13 activity was clearly correlated with the decrease or disappearance of the inhibitor activity. Combination of rituximab and vincristine therapy would appear to be very effective against refractory TTP.