BACKGROUNDrnHBV and HIV are the two most important viral infectious agents which share common modes ofrntransmission and which can seriously affect the health of both the pregnant women and her baby.rnVertical transmission of HBV from the mother to her baby is the most important modes ofrntransmission in Africa. Neonates who contract the virus from their mother have more thanrn90% chance of becoming chronic carriers and this can be prevented by vaccinating the babyrnimmediately after delivery.There are only few studies on the prevalence and rate of verticalrntransmission of HBV during pregnancy in Addis Ababa.rnOBJECTIVErnTo determine the seroprevalence of HBsAg during pregnancy and its rate of verticalrntransmission.rnMETHODSrnA cross sectional study was conducted from May to September 2014 in three teaching hospitalsrnin Addis Ababa. A total of 530 pregnant women were included in the study. Sociodemogrhaphicrnfactors and explanatory variables were collected with structured questionnaire. HBsAg wererntested with ELISA and HIV was tested by Rapid test kits following national HIV test algorithms.rnThe mothers with HBsAg positivity were also tested for HBeAgand followed till they deliverrnand cord blood was tested for HBsAg with ELISA.rnRESULTSrn24/530(4.5%) were tested positive for HBsAg and of these 2(8.3%) were also positive forrnHBeAg. Of mothers with HBsAg 4(16.7%) were also positive for HIV. 17/530(3.2%) wererntested positive of HIV and 4(23.5%) were also positive for HBsAg. Being single pregnantrnwomen (AOR=6,95CI,1.5-22.8) and having HIV (AOR=5.6,95CI,1.4-22.1) has statisticallyrnsignificant relationship with Positivity for HBsAg. Having HBsAg was the only variablernassociated with having HIV (AOR=6, 95CI, 1.7-21.5). All cord blood tested for HBsAg werernnegative.rnCONCLUSSIONSrnThe prevalence of HBV among pregnant mothers in Addis ababa is of intermediate endemicity.rnThe prevalence of HIV among pregnant women of Addis ababa is 3.2% and 16.6% of thosernmothers with HBV also has HIV.Single pregnant women and those pregnant women with HIV were more likely to test positive for HBsAg.There was no perinatal transmission in this studyrnand the perinatal outcome of pregnant women with HBsAg seems to be not adversely affected