The risk of perinatal B virus transmission is estimated in France on results of limited studies carried out during a long period and essentially in metropolitan area. Systematic screening for HBsAg in pregnancy was decided in February 1992 in France. In order to obtain national data on HBsAg prevalence of pregnant women, the authors have summarized the results obtained from twelve French university hospitals during one year. Among the 21,476 pregnant women studied (French: 16,351 and immigrant: 5,125), the total HBsAg prevalence was 0.72% and was significantly higher in the immigrant women group (2.56%) when compared to that of French women (0.15%). The HBsAg prevalence increased from Mediterranean area (1.75%) to SubSaharan Africa (4.61%) and South East Asia (5.45%). Important variations were observed between the centers (from 0.13 to 2.99%). Among the HBsAg carriers, 16.5% were HBeAg and/or HBV-DNA positive in their serum. The only means to prevent each year in France around 850 chronic HBV infections by vaccination of the neonates consist in systematic HBsAg screening.