In order to investigate the change of glutathione concentration in BAL from the patients with diffuse interstitial lung disease. We measured the levels of glutathione in BAL from the patients with interstitial lung disease, including idiopathic interstitial pneumonitis (IIP), hypersensitivity pneumonitis (HP), collagen disease with pneumonitis, and sarcoidosis. The result showed that the glutathione concentration in BAL of the patients with IIP, HP, collage disease with pneumonitis, were significantly lower than that of the control group, but compared with the control group, the glutathione concentration of the patients with sarcoidosis did not show significant difference. The results may provide further insight into the pathogenesis of oxidant-induced interstitial lung disease and its therapy.