BACKGROUND: Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) is a disease entity defined by the presence of thrombocytopenia and microangiopathic hemolytic anemia with or without fever, neurologic and renal symptoms. Therapeutic plasma exchange (TPE) has proven to be an effective treatment for TTP/HUS and has decreased mortality. We evaluated the effectiveness of TPE for TTP/HUS at the Department of Clinical Pathology, Samsung Medical Center during the last 6 years. METHODS: We assessed retrospectively the chief complaints, the clinical course, the treatment and the outcome in 17 TTP/HUS patients treated with TPE from December 1994 to May 2001. Minimal diagnostic criteria for TTP/HUS were unexplained thrombocytopenia and microangiopathic hemolytic anemia, with or without fever, neurologic, and renal symptoms. The range of ages of the patients was 15 to 63 years and the female to male ratio was 2:1. RESULTS: The most frequent clinical presentation was a renal problem (71%), followed by fever (53%) and neurologic symptoms (24%). The causes of TTP/HUS followed in the order of frequency: idiopathic (41%), suspicious for Escherichia coli O157: H7 infection (24%), systemic lupus erythematosus (18%), mitomycin C induced (12%), and preeclampsia (6%). A total of 229 TPE procedures were performed for 17 patients (mean: 13 procedures). The replacement fluids for TPE were fresh frozen plasma (59%) and cryosupernatant (41%). Thirteen patients (76%) survived and three of them relapsed (23%); however, they responded to further treatment. In comparing the laboratory results between pre and post TPE, significant changes were found in the white blood cells and platelet counts, creatinine, total bilirubin, and lactic dehydrogenase. The initial symptoms did not indicate a recurrence rate and a variety of drugs were used, except for corticosteroid administration. CONCLUSIONS: TTP/HUS patients responded well to TPE. The overall efficacy of TPE for TTP/HUS was 76%. The causes of TTP/HUS, the administered drugs and the replacement fluid did not affect the patient's prognosis.