Atypical hemolytic uremic syndrome (HUS) associated with factor H deficiency (FHD) carries a poor prognosis. A 3-year-old girl with FHD-HUS reached end-stage renal disease at age 6 months after experiencing numerous relapses; she underwent a cadaveric renal transplant at age 46 months. One month after transplantation, she experienced an extensive non-hemorrhagic cerebral infarction. Later, hematologic and renal manifestations of HUS developed, followed by another massive cerebral infarction and death in spite of multiple plasma transfusions. A 14-month-old boy with FHD-HUS experienced numerous HUS episodes starting at the age of 2 weeks. Daily plasma transfusions during relapses brought about only a temporary state of remission. However, prophylactic twice-weekly plasma therapy has been successful in preventing relapses and preserving renal function. With this regimen, serum factor H was increased from 6 mg/dL to subnormal values of 12 to 25 mg/dL (normal >60 mg/dL). We conclude that FHD-HUS recurs because FHD is not corrected by renal transplantation. A hypertransfusion protocol may prevent FHD-HUS.