SUMMARY Japanese patients with chronic hepatitis C infection unresponsive to treatment with interferon possessed genotypes disproportionately conferring low mannan-binding lectin (MBL) concentrations. Our aims were to confirm or refute this finding in European patients at the MBL protein level, and to investigate whether a low circulating concentration of MBL might influence susceptibility to, or disease progression from, hepatitis C viral infection. Serum samples obtained from 180 hepatitis C patients and 566 blood donors were assayed for MBL. MBL concentrations were related to disease characteristics retrieved from patients’ records. MBL concentrations were higher in hepatitis C patients (median 2·5 µg/ml versus 1·3; P < 0·0001) and the proportion of patients with very low (MBL-deficient) concentrations was similar to that of the healthy controls. There were no significant associations between patients with low serum MBL and the disease features studied, including response to antiviral therapy. Therefore, low circulating MBL does not increase susceptibility to hepatitis C infection, and MBL concentration does not have a major influence on the course of the disease or the response to antiviral therapy. MBL replacement therapy would therefore not be indicated for chronic hepatitis C patients who failed to respond fully to treatment with interferon and ribavirin.