The relationship between donor status for antibody to hepatitis B core antigen and the occurrence of non-A, non-B posttransfusion hepatitis in the recipient was prospectively studied in 112 patients undergoing open-heart surgery who were followed for 6.5 months after surgery. Non-A, non-B posttransfusion hepatitis occurred in five (7.93%) of 63 patients who had received at least one anti-HBc-positive blood unit compared to seven (14.28%) of 49 patients who received anti-HBc-negative blood only. Statistical analysis revealed that the incidence of non-A, non-B posttransfusion hepatitis was independent of the use of blood positive for anti-HBc. Based upon these results and the high prevalence (17.3%) of anti-HBc among our blood donor population, the exclusion of anti-HBc-positive blood does not seem appropriate to achieve a reduction in the incidence of non-A, non-B posttransfusion hepatitis.