Thrombotic thrombocytopenic purpura (TTP) is a syndrome characterized by microangiopathic hemolytic anemia, thrombocytopenia, neurologic abnormalities, fever and renal dysfunction. Prior to modern therapy, fewer than 3% of patients survived. However, with plasmapheresis, up to 82% of patients survive. We report a case of recurrent TTP which proved fatal despite plasmapheresis. At autopsy the hyaline thrombi found were notably smaller and of shorter duration than those of untreated TTP. These findings suggest that therapy had brought about an abatement of the microthrombotic process in spite of the fatal outcome.