To describe the clinical and immunologic patterns of disease expression of patients with chronic hepatitis C virus (HCV) infection and positive antimitochondrial antibodies (AMA). We investigated the presence of AMA in 237 consecutive HCV patients with extrahepatic manifestations from an International Registry. AMA were detected by indirect immunofluorescence in triple rat tissue (liver, stomach and kidney), aceton-fixed criosections and FITC-conjugated rabbit anti-human immunoglobulins. We found positive AMA in 18 (8%) out of 237 HCV patients. All patients were female with a mean age at protocol inclusion of 65.8 years (ranging from 37 to 87 years). Twelve (67%) patients fulfilled classification criteria for systemic autoimmune diseases (SAD), including Sjögren's syndrome (n = 7), systemic sclerosis (n = 3) and systemic lupus erythematosus (n = 2). Fourteen (78%) of the HCV-AMA patients presented at least one of the highly suggestive characteristics of primary biliary cirrhosis (PBC): 9 (50%) had a specific M2 pattern, 6 (33%) had more than twice normal levels of alkaline phosphatase, 5 (28%) had raised IgM levels and 4 (22%) a histological pattern compatible with PBC. Five (28%) patients developed neoplasia after detection of AMA. Seven (39%) patients died, due to neoplasia (n = 4), cirrhotic complications (n = 2) and hepatopulmonary syndrome (n = 1). We describe a subset of HCV patients with positive AMA who presented a broad spectrum of clinical features, including liver, autoimmune and neoplasic manifestations. Two-thirds of these patients presented an associated SAD, mainly Sjögren's syndrome or systemic sclerosis, together with a high frequency of multiple autoantibodies and an increased prevalence of cirrhosis and neoplasia.