Hepatitis C virus (HCV) has been found in the serum of 3 out of 109 patients with Sjögren's syndrome, whereas Sjögren's syndrome has been demonstrated in 3 out of 7 HCV-positive patients. The six HCV-positive Sjögren's syndrome patients were compared with 95 HCV-negative Sjögren's syndrome patients. Anti-smooth muscle antibodies were detected in 1 of the former group and 6 of the latter. Cryoglobulin existed in 1 and 6, respectively. The levels of circulating IgA and IgA-containing immune complexes were lower in the HCV-positive than in the HCV-negative patients.