In pregnant women and children, the hepatitis B virus can cause acute or chronic hepatitis or liver cirrhosis. Perinatally-acquired infection causes persistent infection in 90% of cases and can be avoided through administration of the hepatitis B vaccine and specific immunoglobulin in the first day of life. Prevention of mother-to-child transmission requires screening for hepatitis B surface antigen (HBsAg) in pregnant women to identify which newborns should be immunized. In some countries this strategy is substituted by universal vaccination of neonates. In infected children, inactivation of viral replication with conversion of HBeAG-positive to anti-HBe-positive status usually occurs. If this seroconversion does not take place and necroinflammatory activity persists in the liver, the use of antiviral agents such as interferon or nucleoside and nucleotide analogs is warranted.