Hepatitis C virus (HCV) infection is emerging as an extremely common and insidiously progressive liver disease that is often associated with several extrahepatic manifestations. In 1992, a possible relationship between Sjögren syndrome (SS) and patients with HCV infection was first postulated. Subsequently, several studies demonstrated that a "true" SS, with similar clinical and histologic features to those observed in primary SS, may occur in some patients with chronic HCV infection. We report the clinical and immunologic characteristics of 35 patients with chronic HCV infection and a well-documented diagnosis of SS. Compared with 60 patients with primary SS who tested negative for HCV antibodies, SS-HCV patients showed a higher mean age (65.9 yr versus 61.5 yr, p = 0.04), a lower prevalence of parotidomegaly (17% versus 47%, p = 0.004), and a higher prevalence of liver involvement (94% versus 3%, p < 0.001). Moreover, those patients with HCV-related SS showed a higher prevalence of anti-parietal cell gastric antibodies (31% versus 13%, p = 0.03), antimitochondrial antibodies (14% versus 2%, p = 0.02), cryoglobulinemia (60% versus 10%, p < 0.001), hypocomplementemia (60% versus 8%, p < 0.001), and a lower prevalence of anti-Ro/SS-A (17% versus 38%, p = 0.03). The "true" SS observed in some patients with HCV may be considered 1 of the extrahepatic manifestations of HCV, and we suggest that HCV infection can be considered as an exclusion criterion for the diagnosis of primary SS.