The data on reactivation of sarcoidosis during treatment with interferon-alfa is unsatisfactory. We here report the case of a female patient with a history of sarcoidosis more than 20 years ago. Due to chronic hepatitis C the patient was treated with pegylated interferon-alfa and ribavirin. Beginning in the 32(nd) week, the patient developed a reactivation of sarcoidosis. The antiviral therapy was continued until week 48 without administration of systemic steroids. Six month after the end of antiviral treatment the sarcoidosis was in remission and the hepatitis C was cured.