Idiopathic pulmonary fibrosis is a chronic disorder characterized histopathologically by a pattern of usual interstitial pneumonia, with heterogeneous and mutilating interstitial fibrosis with foci of proliferating fibroblasts, honeycomb lung, and little if any inflammation. The diagnosis is based on a pluridisciplinary analysis of the clinical symptoms, the chest high-resolution computerized tomography features, and pathology on video-thoracoscopic lung biopsy when indicated. In half of the cases, the typical tomodensitometric pattern allows to make a confident diagnosis without a lung biopsy. The median survival is only about 3 years and is presently not improved by any treatment. Treatment with N-acetylcysteine (antioxydant) in association with corticosteroids and azathioprine may slightly reduce the rate of functional worsening. Clinical trials are in progress to improve the treatment of this still incurable disease.