An increased prevalence of hepatitis C virus (HCV) infection in patients with diabetes mellitus has suggested a link between these two conditions and the possibility of patient-to-patient HCV transmission during hospital admissions in diabetes units. We investigated the prevalence of HCV antibodies in 259 patients with diabetes mellitus consecutively admitted to our diabetic unit in 1998. The control group was composed of 14,100 volunteer blood donors. We divided the diabetic patients into two groups according to their HCV antibody status and also analysed patients for the following variables: age, disease duration, diabetes treatment, previous hospital admissions in a diabetes unit and use of finger stick devices. Anti-HCV antibodies were detected in 8 diabetic patients and 6 blood donors (3.09% vs 0.04%, p < 0.001). No differences were observed between anti-HCV-positive and anti-HCV-negative diabetic patients in terms of mode of treatment, previous hospital admissions in a diabetic unit and use of finger stick devices for capillary blood sampling. Our findings indicate that these medical practices play no role in nosocomial transmission of HCV in diabetic patients.