Since November 1989, Japanese Red Cross blood centres throughout the country have screened donors for hepatitis C virus (HCV) with an Ortho enzyme-linked immunosorbent assay for antibody to the C100-3 viral peptide. Simultaneously, the centres started to screen for units with high-titre (greater than or equal to 2(6)) antibody to hepatitis B virus core antigen (HBcAb) in the absence of hepatitis B virus surface antigen and antibody. To test the effectiveness of this policy, the incidence of post-transfusion non-A, non-B hepatitis (PTNANBH) and post-transfusion hepatitis B (PTHB) after screening had been introduced (November, 1989, to December, 1990, inclusive) was compared with the incidence before screening (January, 1988, to October, 1989, inclusive). Incidence of PTNANBH in patients who had received 1-10 unit transfusions was 4.9% (58/1189) before screening vs 1.9% (15/784) afterwards. Incidence in those who had 11-20 unit transfusions was 16.3% (64/392) vs 3.3% (4/124). Incidence of PTHB was 0.25% (4/1597) before screening; no cases have been detected subsequently. These results show the effectiveness of the first-generation anti-HCV test and indicate the value of screening for high-titre HBcAb in addition to HBV surface antigen testing in HBV endemic areas.