The postpartum use of plasma exchange with fresh-frozen plasma was assessed in a group of seven women with severe preeclampsia-eclampsia and HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count) that persisted greater than 72 hours after delivery. During the study interval in which a total of 107 gravid women with HELLP syndrome were seen in our referral center, these seven patients (6.5%) demonstrated persistent thrombocytopenia (platelet count usually less than 30,000/mm3), rising lactic dehydrogenase (greater than 1000 IU/L) and evidence of multiorgan dysfunction. The seven case histories emphasize the variety of clinical and laboratory profiles that can be encountered in this small group of gravid women at risk for severe morbidity or mortality. Up to three 3 L plasma exchanges were required to effect permanent disease arrest and reversal. Utilization of the IBM 2997 Cell Separator system permitted bedside performance of procedures with enhanced convenience and optimal medical management. Successful plasma exchange was associated with (1) sustained increases in the mean platelet count at 24, 48, and 72 hours that were 2.2, 3.6, and 4.5 times the preexchange platelet counts and (2) a decreasing trend in lactic dehydrogenase concentrations below 1000 IU/L within 48 hours of exchange plasmapheresis. The current series of patients supports our recommendation that a trial of plasma exchange(s) with fresh-frozen plasma be considered for treatment of the infrequent postpartum case of HELLP syndrome that fails to abate within 72 hours of delivery and in which other evidence develops of an ongoing, widespread, and life-threatening thrombotic microangiopathy.