Since 2004, pegylated interferon (P-IFN) in combination with ribavirin has become the optimal choice of therapy for chronic hepatitis C virus (HCV) infection. IFN a-2b suppresses HCV replication and restores elevated serum aminotransferase levels, leading to improvements in the histological changes in the livers of patients with chronic hepatitis C. 1 Unfortunately, P-IFN has several adverse effects, including pneumonitis. This complication has been reported in the treatment of malignant diseases and CHC. 2 We report a patient with interstitial pneumonitis thought to be caused by an IFN-based treatment in an unusual scenario of a patient with HCV-related Child–Pugh stage A cirrhosis, who experienced dyspnea, fever, and cough after 12 months of treatment with P-IFN a-2b. Her lung injury and pulmonary symptoms did not disappear despite discontinuation of IFN and the administration of corticosteroid. We concluded that the patient developed a fatal interstitial pneumonitis associated with P-INF a-2b therapy.