As we know horizontal transmission of hepatitis B virus (HBV) without apparent sexual or parenteral exposure is common in hyperendemic areas. In most cases, the route of transmission is unknown. Vertical, sexual and parenteral transmission of HBV has been well documented, however horizontal transmission without apparent parenteral exposure is a common mode of acquisition among very small and preadolescent children. This route applies especially to high endemicity settings. In areas of low HBVendemicity, horizontal transmission may explain secondary cases of HBV among households and day care centers that have a persistant carrier.