The aim of this study was to compare the socio-demographic characteristics and risk factors in anti-HCV positive blood donors with those of matched controls. The participants were 50 hepatitis C antibody (HCV) positive blood donors and 50 matched blood donors with no evidence of HCV infection, who gave blood to the South Western Transfusion Centre between November 1991 and July 1992. A confidential structured interview was conducted to collect socio-demographic data and to elicit information on risk factors for HCV. Measurements were made of the prevalence of risk factors and socio-demographic characteristics in cases and controls. The main results were that 45 of the 50 cases could have been exposed to HCV by previous intravenous drug abuse (IVDA), blood transfusion or medical employment. Cases were significantly more likely to have a history of IVDA, tattooing or of medical employment than matched controls. Cases with no history of IVDA were significantly more likely to have had a blood transfusion. The key conclusions to emerge are that current policies are ineffective at excluding those with a history of IVDA from the donor pool. Consideration should be given to the introduction of a policy of direct confidential questioning about risk factors for all donors, or, at a minimum, the use of a questionnaire.