HBeAg/anti-HBe and Dane particle-associated DNA polymerase activity were detected in serum samples from 358 HBsAg asymptomatic carriers found during normal routine screening of 11,200 blood donors (HBsAg prevalence 3.1%). Since virus specific DNA polymerase activity and HBeAg seem to be associated in some way with hepatitis B virus infectivity and liver damage, 5% of the HBsAg carriers examined, as detected by the presence of HBeAg, and 9.5%, as shown by DNA polymerase activity, can be expected to have liver damage and a potential risk of transmitting hepatitis B to contacts. On the other hand, 48% of subjects were theoretically healthy and non-infective because of the presence of anti-HBe in their blood. The differentiation of groups of asymptomatic HBsAg carriers, on the basis of these serological markers, may have important clinical and epidemiological implications.