The aim of our report is to present our 11-year experience with therapeutic membrane plasma exchange therapy for the treatment of idiopathic thrombotic thrombocytopenic purpura syndrome (TTP). In 56 patients, membrane plasma exchange therapy was initiated immediately and performed once or twice daily until the platelet count normalized. During each plasma exchange procedure, 1-1.5 plasma volumes (3606 +/- 991 mL) were replaced with fresh frozen plasma. In 37 females and 19 males (44 +/- 21 years), 1066 plasma exchange procedures were performed. The average duration of treatment was 23 +/- 17 days. The average number of plasma exchanges was 19 +/- 17 per patient. Renal impairment was detected in 36% of patients. At the initiation of plasma exchange treatment, the average platelet count was 31 +/- 30 x 10(9)/L and reached 199 +/- 95 x 10(9)/L thereafter. Fifty-two of 56 (93%) patients demonstrated an excellent response to plasma exchange therapy, of whom 48 patients (86%) attained complete remission with a platelet count of more than 100 x 10(9)/L. Four patients died soon after the initiation of plasma exchange therapy, when only 1-3 procedures had been performed. During the follow-up period, six patients with complete remission had 1-5 subsequent relapses each year. One of them died of acute hemolytic reaction during the tapering of plasma exchange procedures. Three patients underwent additional splenectomy. Our experience with primary TTP supports the plasma exchange treatment with fresh frozen plasma as a mandatory, up-to-date therapy. Close monitoring during all 1066 procedures showed no serious side-effects.