A total of 14,366 one-time blood donors were examined; 984 (6.8%) donors of them were found to have anti-HBc. All anti-HBc-positive samples were tested for HBsAg, IgM anti-HBc, HBeAg, anti-HBe, and specific DNA-HBV by polymerase chain reaction (sensitivity 400 coplml or higher). Anti-HBc in combinations with HBsAg, anti-HBe, IgM anti-HBc was detected in 29 (2.9%), 3 (0.3%), 5 (0.5%) donors, respectively. Specific HBV DNA was identified in 29 donors with HBs-antigenemia and in 9 anti-HBc positive donors in the absence of serum HBsAg. The activity of AIAt was correlated with neither HBsAg nor HBV DNA. Thus, latent HBV infection is 0.9% of anti-HBc-positive one-time blood donors and tests for anti-HBc may be useful in identifying persons who need a more meticulous study for HBV DNA.