We report a case of Langerhans' cell histiocytosis (LCH) occurring after a living donor liver transplantation (LDLT) for fulminant hepatitis. A 9-month-old girl underwent an LDLT for fulminant hepatitis of an unknown cause. The histology of the native liver did not show any findings of LCH. On postoperative day 42, her Epstein-Barr virus (EBV)-DNA and cytomegalovirus antigenemia were both found to be positive. As a result, she was treated with antiviral agents and a reduction of the immunosuppression dosage. On postoperative day 98, acute rejection occurred, and she was treated with FK506, methylprednisolone, and finally, anti-CD3 murine monoclonal antibody was added. Subsequently, the EBV was re-activated. Thereafter, skin eruptions, swelling of the systemic lymph nodes, and pancytopenia appeared on postoperative day 127. LCH was diagnosed based on the typical histological findings as LCH, CD1a, and S-100positive cells in her skin and a lymph nodes biopsy. She was treated by chemotherapy. The symptoms disappeared a few weeks after the start of the chemotherapy, and a clinical remission of LCH was obtained. We could not detect any evidence of EBV infection in the tumor cells. In spite of the fact that her LCH lesions thereafter remained in remission, she died of hepatic failure at 22 months after undergoing the liver transplantation. In conclusion, we discuss the factors influencing the occurrence of LCH in our patient after LDLT, while also evaluating the relationship between LCH and the immunosuppressive therapy administered to this patient. (Liver