OBJECTIVES: Mixed cryoglobulinaemia (MC) is a systemic vasculitis frequently associated with hepatitis C virus (HCV) infection. A possible link between HCV infection and type 2 diabetes has been suggested. This study evaluated the prevalence and clinical phenotype of diabetes in MC-HCV+ patients. METHODS: Two hundred and twenty-nine consecutively recruited MC-HCV+ patients were compared with 217 sex- and age-matched controls without HCV infection. RESULTS: The prevalence of type 2 diabetes was significantly higher in MC-HCV+ patients than in controls (14.4 vs 6.9%, P < 0.01). Diabetic MC-HCV+ patients were leaner than diabetic patients without MC-HCV (P < 0.0001), and showed significantly lower total and low-density lipoprotein cholesterol levels (P < 0.001) and lower systolic (P = 0.01) and diastolic blood pressure (P = 0.005). MC-HCV+ diabetic patients had non-organ-specific autoantibodies more frequently (34 vs 18%, P = 0.032) than non-diabetic MC-HCV+ patients. CONCLUSIONS: The prevalence of type 2 diabetes is higher in patients with MC-HCV than in controls. Diabetic MC-HCV+ patients show an attenuated diabetic phenotype and are more likely to carry non-organ-specific autoantibodies.