Lamivudine is a cytidine analogue reverse transcriptase inhibitor that is active against HIV-1, HIV-2, and HBV; it is approved for HIV in adults and in children aged 3 months or older. Lamivudine enter cells by passive diffusion and is phosphorylated to lamivudine 5’-triphosphate which is the active anabolite. Lamivudine is administered orally, its oral bioavailability is 86%, and lamivudine is primarily excreted unchanged in the urine. Lamivudine may be administered alone but in most cases it is co-administered with other antiviral drugs. The oral dose of lamivudine is 4 mg/kg twice-daily in infants, and in children it is computed according to the child age and body-weight and the maximum dose is 300 mg once-daily. Lamivudine co-administered with antiviral drugs has been found efficacy and safe in infants and children with HIV-infection and lamivudine prevents the transmission of hepatitis B virus from mother-to-infant. Lamivudine elimination half-life is about 6 hours in infants and about 4 hours in infants and children. The prophylaxis and treatment with lamivudine have been studied in infants and children. The prophylaxis and treatment often consist in lamivudine co-administered with other antiviral drugs such as nevirapine, lopinavir/ritonavir or zidovudine. Lamivudine freely crosses the human placenta and freely migrates into the breast-milk. The aim of this study is to review the lamivudine dosing, efficacy, safety, prevention of mother-toinfant transmission of hepatitis B virus, pharmacokinetics, interaction with drugs, prophylaxis, and treatment in infants and children, the transfer across the human placenta and the migration into the breast-milk.