A 71-year-old woman with fever and dry cough was admitted to our hospital. Chest computed tomography, bronchoalveolar lavage and transbronchial lung biopsy were performed, and bronchiolitis obliterans organizing pneumonia (BOOP) was diagnosed. The patient was treated with corticosteroid, and marked improvement was noted. However, when the dosage was tapered, the BOOP recurred. We increased the dosage of corticosteroid and also put the patient on a daily regimen of cyclosporin. The cyclosporin was administered orally, and was effective, so that we could gradually decrease the dosage of corticosteroid. We concluded that cyclosporin may be useful in the treatment of refractory BOOP.