Insulin resistance (IR), glucose intolerance and diabetes mellitus are commonly associated with cirrhosis. The exact pathogenetic mechanisms responsible are still unknown; however, they may be related to both hepatitis C virus itself and to liver injury. IR may be the earliest abnormality, which in the following years may progress to clinical diabetes mellitus. The aim of this study was to investigate the presence of IR by euglycaemic hyperinsulinemic clamp technique, in chronic hepatitis C patients. 15 patients and nine healthy controls without any known condition that may affect IR were enrolled to the study. Chronic hepatitis C was diagnosed by liver biopsy (hepatic activity index was also determined in 10 patients) and appropriate viral and biochemical tests. Eight patients were given interferon therapy, which had been stopped for at least 3 months before the study. Euglycaemic hyperinsulinemic clamp technique was performed as previously described and peripheral glucose utilisation rate, M value, was calculated in mg/kg/min by infusion of 40 IU/m2/min regular insulin. M value of the control group was significantly higher than that of chronic hepatitis C patients (M = 5.1+/-1 vs. 3.7+/-1; p = 0.004), which was consistent with IR in the patient group. There was no significant correlation between the M value and alanine aminotransferase, aspartate aminotransferase and hepatic activity index (p = 0.621, 0.549, 0.479, respectively). Our results suggest that IR is present in chronic hepatitis C patients; it is not directly related to hepatic injury, moreover, it may be associated with some component(s) inherent to hepatitis C virus.