Group B streptococcus is a possible cause of chorioamnionitis, endometritis and urinary tract infections in pregnant woman. Maternal risk factors and the vertical transmission of GBS and neonatal GBS infection occur through the following fever during labor, the rupturing of membranes more than 18 hours before delivery, prematurity and chorioamnionitis. GBS can induce early-onset neonatal disease (sepsis, meningitis or pneumonia) during the first week of life and late-onset neonatal infection (leptomeningitis) within the first 12 weeks of life. Numerous strategies for preventing neonatal group B streptococcal infection were investigated: 1) the treatment of GBS-colonized women during the third trimester of pregnancy did not prove to be effective because it does not reduce maternal colonizzation rates at delivery; 2) the neonatal universal post-partum prophylaxis with penicillin G was ineffective and increased neonatal mortality due to penicillin-resistant bacterial infection; 3) the intrapartum maternal chemoprophylaxis with penicillin G or ampicillin in GBS-colonized women, in women with risk factors, or in women with both GBS colonization and risk factors. The latter strategy proved to be the most effective because it reduces the risk of early-onset GBS infection by 75% and 95% when associated with post-neonatal prophylaxis. To date, there are no guidelines on the management of the asymptomatic neonate whose mothers have been treated with chemopropylaxis intra-partum.