A retrospective study was undertaken to identify recipients of blood from donors subsequently shown to be positive for hepatitis C virus using second-generation tests and polymerase chain reaction. The main aims were to determine the numbers of such recipients who were still alive and traceable, and to determine the risk of infection in this group. The feasibility and workload of this procedure, which is currently not practised in the U.K. or U.S.A., was also assessed. In the first six months of routine testing 42,697 donors were tested. Of 20 confirmed to be HCV-positive, 15 were regular donors. Eighty-three components were prepared from 63 anti-HCV positive previous donations from these donors. In all, nine recipients were found to be alive. All were positive for anti-HCV. We conclude that although this retrospective procedure is time-consuming and difficult, substantial numbers of infected recipients can be identified. The availability of treatment for chronic hepatitis C for such patients should encourage transfusion services to reassess current policies on the hepatitis C retrospective.