Background. Hepatitis B is a major public health problem in the developing countries of Africa and Asia because the prevalence of HBs antigen carriers is high. In Ivory Coast, the prevalence of HBs antigen carriers is more than 8% (6 to 29%). In these countries, in which hepatitis B is highly endemic, most infections with hepatitis B virus (HBV) occur during early childhood. The chronic carriage of HBV was found to be common in children, who played a key role in maintaining the high level of endemicity in these areas. Vaccines against HBV are effective and their introduction as part of the Expanded Program of Immunization (EPI), as recommended by the WHO, is feasible. Objective. The aim of this study was to evaluate the prevalence of HBs antigen in pregnant women and to determine the rate of maternal transmission of HBV to the fetus, to demonstrate the importance of HBs antigen screening during pregnancy and the immunization of babies in the Ivory Coast. Patients and methods. Between August 1995 and February 1996, 395 women in the last three months of pregnancy (age 25 6.9 years) were screened for HBs antigen. Those testing positive were also screened for HBe antigen. Transmission of HBV in utero was studied with 322 mothers and their offspring. HBs antigen was assayed in the cord blood of the offspring of HBs antigen-positive mothers. If the test for HBs antigen was positive, HBe antigen was also assayed. Second-generation ELISA tests (MONOLISA HBs Ag and MONOLISA HBe Ag from Sanofi Pasteur) were used. Babies from HBs antigen-positive mothers were vaccinated at birth with three doses of GenHevac B.