Methotrexate may cause methotrexate-associated lymphoproliferative disorder (MTX-LPD)
however, this disease is uncommon in the gastrointestinal tract. We examined six patients with MTX-LPD in the gastrointestinal tract at our hospital. All of the lesions were ulcerative. Four cases regressed spontaneously, all of which were positive for Epstein-Barr virus-encoded small RNA by in situ hybridization. Two patients who did not regress were negative for Epstein-Barr virus RNA, one of whom received chemotherapy, and one underwent surgery. The prognosis of this disease is considered to be good. MTX-LPD should considered when ulcerative lesions are observed during endoscopy in patients receiving MTX.