Lung toxicity associated with cyelophosphamide use is a rare but serious side effect, that may result in a fatal course. However no such cases have been reported in Korea, so clinicians would not be alert to this adverse effect. We recently experienced a woman with Wegener´s granulomatosis and idiopathic pulmonary fibrosis. This patient had been administered 12 grams of cyclophosphamide for 4 months. At that time of admission, She felt aggravating dyspnea on exertion for 2 weeks. Her chest x-ray and high resolution CT revealed aggravated reticular opacities and ground glass appearances. Dyspnea va;as improved and ground glass appearances on HRCI was disappeared after discontinuation of cyclophosphamide. We diagnosed this case as cyclophosphamide-induced pneumonitis and report it with a brief review of the literature.