Interstitial pneumonitis(IP) is an uncommon pulmonary complication associated with interferon(IFN) therapy for chronic hepatitis C virus(HCV) infection.Pneumonitis can occur at any stage of HCV treatment,ranging from 2 to 48 wk,usually in the first 12 wk.Its most common symptoms are dyspnoea,dry cough,fever,fatigue,arthralgia or myalgia,and anorexia,which are reversible in most cases after cessation of IFN therapy with a mean subsequent recovery time of 7.5 wk.Bronchoalveolar lavage in combination with chest high resolution computed tomography has a high diagnostic value.Prompt discontinuation of medication is the cornerstone,and corticosteroid therapy may not be essential for patients with mild-moderate pulmonary functional impairment.The severity of pulmonary injury is associated with the rapid development of IP.We suggest that methylprednisolone pulse therapy followed by low dose prednisolone for a short term is necessary to minimize the risk of fatal pulmonary damage if signs of significant pulmonary toxicity occur in earlier stage.Clinicians should be aware of the potential pulmonary complication related to the drug,so that an early and opportune diagnosis can be made. Interstitial pneumonitis (IP) is an uncommon pulmonary complication associated with interferon (IFN) therapy for chronic hepatitis C virus (HCV) infection. .Its most common symptoms are dyspnoea, dry cough, fever, fatigue, arthralgia or myalgia, and anorexia, which are reversible in most cases after cessation of IFN therapy with a mean subsequent recovery time of 7.5 wk.Bronchoalveolar lavage in combination with chest high resolution computed tomography has a high diagnostic value. Prompt discontinuation of medication is the cornerstone, and corticosteroid therapy may not be essential for patients with mild-moderate pulmonary functional impairment. severity of pulmonary injury is associated with the rapid development of IP.We suggest that methylprednisolone pulse therapy followed by low dose prednisolone for a short term is necessary to minimize the risk of fatal pulmonary damage if signs of si gnificant pulmonary toxicity occur in earlier stage. Clinicians should be aware of the potential pulmonary complication related to the drug, so that an early and opportune diagnosis can be made.