A case of severe autoimmune hemolytic anemia after ABO matched living donor liver transplantation. We present here a case of severe autoimmune hemolytic anemia after ABO matched living donor liver transplantation. The patient is 56 y.o male. He received living donor liver transplantation from his ABO matched son in May 2007. In July, he was suffered from a progressive anemia, and diagnosed as autoimmune hemolytic anemia by the laboratory examinations. Intensive treatment including predonisolone, azathiopurine, rituximab, plasma exchange, was given, however, the disease was resistant to the treatment. By the administration of cyclophosphamide combined with rituximab, remission was finally achieved. To date, immune mediated hemolytic anemia after ABO matched living donor liver transplantation has not been reported, although several cases of ABO mismatched living donor liver transplantation have been reported. His severe but transient clinical course of anemia suggests that the transient emergence of donor lymphocytes may be responsible for onset of hemolytic anemia.