Postpartum hemolytic uremic syndrome (HUS) is described in a woman with a history of spontaneous abortions and both circulating lupus anticoagulant and anticardiolipin antibody (ACA). After termination of her pregnancy because of severe preeclampsia, ACA blood levels increased simultaneously with the onset of a microangiopathic process associated with severe hypertension and renal failure. Plasma exchange resulted in a rapid decline in ACA levels and immediate improvement in her clinical condition. This case strongly suggests an important causal relationship between ACA and postpartum HUS. The possible mechanisms of ACA-related postpartum HUS and the potential role of plasmapheresis in its treatment are reviewed and discussed.