We report on a patient of rheumatoid arthritis (RA) who sequentially developed an axillary mass and a fatal interstitial pneumonia during a 2-year course of methotrexate (MTX) therapy. Autopsy revealed a systemic lymph node involvement and the diagnosis of Epstein-Barr virus (EBV)-related lymphoproliferative disease (LPD) with the features of lymphomatoid granulomatosis was made. The lung tissue specimens revealed a typical diffuse alveolar damage (DAD), and small nodules consisting of atypical B lymphocytes showing positive staining for EBV were sparsely recognized only in basal lungs. This is the first report of a RA patient receiving MTX therapy sequentially developing MTX-associated lymphomatoid granulomatosis and DAD.