The study describes the clinical, virologic and immunological characteristics of a patient with interstitial pulmonary fibrosis during interferon treatment for HCV chronic hepatitis. After the interruption of the interferon and the beginning of immunosuppressive treatment, an improvement of pulmonary pathology was observed. At the reintroduction of interferon, the patient presented a rapid worsening of pulmonary fibrosis with a normalization of biochemical and virologic parameters of hepatitis. The correlation among interstitial pulmonary fibrosis, HCV infection and interferon treatment is discussed; however in the described case, the pulmonary pathology was correlated to interferon treatment.