OBJECTIVE To study if it is necessary to screen for core antibody against hepatitis B (anti-HBc) to prevent post-transfusion hepatitis B and what is its criteria for screening. METHODS Relationship between the titer of anti-HBc and HBV DNA in blood from qualified donors by routine testing was conducted. HBV DNA was detected in 297 units of blood with anti-HBc at various titers by immuno-nested polymerase chain reaction (RT-PCR). RESULTS HBV DNA was detected in one of four units of blood with positive anti-HBc at a dilution of equal to or greater than 1:128, and no HBV DNA was detected in other 75 units of blood with a dilution of anti-HBc less than 1:128. There was significant relationship between HBV DNA and the titer of anti-HBc. No HBV DNA was detected in 218 units of blood with both positive anti-HBc and anti-HBs and in 50 units with negative anti-HBc. Detection rate of HBV DNA in blood with positive anti-HBc was only 0.34% (1/297). CONCLUSION Blood containing higher titer of single anti-HBc may be infectious. It is suggested that sensitivity of the reagents for detecting HBsAg currently used (1 ng/ml) be improved with the limited budget.