We report a case of acute interstitial pneumonia (AIP) determined by clinical appearance and pathologic manifestations. The patient was critically ill but survived by intensive treatment. The disease was characterized by fulminate onset and developed to respiratory failture. Its pathologic features as same as those of ARDS, but it is not differentiate AIP from chronic interstitial pneumonia on the basis of etiology. The outcome of AIP was improved by corticosteroid therapy. Relevant literature, history, pathogenesis, pathological features, clinical findings, differential diagnosis, treatment and prognosis of AIP are discussed.