The present communication deals with the results of investigations on the frequency of HBsAg-carriership among expectant mothers in Fergana (the Uzbek SSR) and on the risk for their children to be infected with hepatitis B virus. To detect the markers of hepatitis B virus, the passive hemagglutination test, the enzyme immunoassay, and the radioimmunoassay were used. The incidence rate of HBsAg-carriership among expectant mothers was rather high (5.1 +/- 0.52%) in comparison with the control group (3.5 +/- 0.70%). The detection of HBsAg in children 3 months after their birth, i.e. at the term corresponding to the possible incubation period of hepatitis B, suggested that the children were infected at birth. As noted in the course of this investigation, the risk for a newborn to be infected was directly related to the titer of HBsAg, as well as to the presence of HBeAg, in the blood of the carrier mother. A high detection rate of HBsAg was registered among children born to HBsAg-carrier mothers, which makes it possible to consider these children as a high risk group with respect to hepatitis B virus infection and necessitates the development of the system of antiepidemic and prophylactic measures for preventing newborns to be infected with hepatitis B.