We report the case of a 40-year-old woman diagnosed with interstitial lung disease due to long-term nitrofurantoin therapy. Despite severely distorted bronchiolar architecture and honeycombing confirmed by computed tomography of the thorax, transbronchial biopsy showed a pattern of acute/subacute interstitial pneumonitis and the symptoms and radiographic findings disappeared within 1 month after administration of prednisone. This case shows that nitrofurantoin-induced lung disease may run a benign course and respond favorably to corticosteroids, even when there is radiographic evidence of established lung fibrosis. Transbronchial biopsy might be useful for assessing the reversibility of pulmonary lesions associated with nitrofurantoin.