Idiopathic pulmonary fibrosis (IPF) is a chronic inflammatory interstitial lung disease characterized by an accumulation of alveolar macrophages and neutrophils in the lower respiratory tract, parenchymal injury, and interstitial fibrosis. Although the etiology of IPF is unknown, it has been suggested that viral agents, among which hepatitis C virus (HCV), may be involved in inducing the disease. In patients with chronic hepatitis HCV+ and in those with mixed cryoglobulinemia HCV-associated, HCV may trigger a subclinical lymphocyte alveolitis. Furthermore, pulmonary fibrosis associated with a variety of rheumatic disorders has been reported in 8/300 patients with active chronic hepatitis HCV+. Bronchoalveolar lavage, carried out in 4/8 patients, showed an increased percentage of neutrophils in all of them and a mild increase of lymphocytes in 2 patients. Thoracoscopic lung biopsy was carried out in 2 patients and showed a desquamative interstitial pneumonia; in one case HCV-RNA was found in the pulmonary parenchyma. Although the above observations seem indicate a role for HCV in IFP, further studies are required to define its true importance in the etiopathogenesis of the interstitial lung disease.