In the current study we investigated 213 randomly selected Hungarian patients diagnosed with primary Sjögren's syndrome (SS). All patients were monitored for hepatitis C virus (HCV) infection and 13 were positive. We compared HCV-negative and -positive patients and made observations on how HCV infection alters the clinical and laboratory features of Sjögren's syndrome. On the basis of these findings, we conclude that HCV infection is more frequent in Hungarian SS patients than in the normal population and that the presence of this virus has a disease-modifying effect on SS.