We present a case of EBV-induced cerebral B cell lymphoproliferation of donor origin after HLA-matched allogeneic BMT for AML. The presentation was note-worthy as this 4-year-old girl was grafted after a conditioning regimen without irradiation, with an unmanipulated, HLA-matched graft. Furthermore, the cerebral mass developed long after reduction of immunosuppressive therapy following improvement of severe GVHD. To our knowledge, such cerebral lymphoproliferation, under these transplant conditions, has never been described.