Riluzole has recently been proven as the first effective drug for the treatment of amyotrophic lateral sclerosis (ALS). We report two rare cases of lung injury caused by riluzole therapy in patients with ALS. Chest radiographs showed bilateral lower lobe, dorsal-dominant ground glass opacity, and/or consolidation. A drug lymphocyte stimulation test (DLST) of peripheral blood or bronchoalveolar lavage cells was positive for riluzole. Histopathological examination of lung biopsy specimens revealed lung injury without fungoid granuloma, vasculitis, or diffuse alveolar damage. To the best of our knowledge, this is the first report of riluzole-induced lung injury with positive DLST results.