During HBV infections, HBsAg is the first serological marker which appears and can be detected within 1 to 2 weeks after exposure. The development of symptoms may take the average of 4 weeks. HBsAg persists during the acute phase and clears late in the convalescence period. Presence of HBsAg after six months indicates a chronic HBsAg carrier state. HBsAg assays are used to identify persons infected with HBV and to prevent transmission of the virus by blood and blood products as well as to monitor the status of infected individuals in combination with other hepatitis B serological markers. Testing for HBsAg is part of the screening (antenatal screening, Blood donors) program to identify HBV infected mothers and to prevent perinatal HBV infection by subsequent immunization. The presence of HBs Ag indicates acute infection. Hepatitis B surface antigen (HBsAg) may remain positive in chronic patients. HBsAg Positive individuals are infectious and they can spread the infection. Positive HBc IgM antibodies indicate acute infection. Anti-HBcAg is a nonspecific marker of infection which can indicate acute, chronic or resolved the acute infection. Antibody to HBsAg (anti-HBs) is a marker of immunity and is present after resolution of acute infection, HBeAg levels can be used to monitor the progress of hepatitis B viral infection. During the early phase of hepatitis B viral infection, after the appearance of hepatitis B surface antigen (HBsAg), HBeAg is first detectable marker in the serum. The titers of both HBs Ag and HbeAg antigens rise rapidly during the period of viral replication in acute infection. HBeAg may persist together with HBsAg in chronic hepatitis B viral infection. Chronic hepatitis B patients have no detectable HBeAg in serum but are positive for antibody to HBeAg (anti-HBe), these patients may also be positive for serum hepatitis B virus DNA. In acute infection, during recovery period the HBeAg levels decrease and later become undetectable in the serum and the Hepatitis B envelope antibody (Anti-HBe) appears. Anti-HBe remains detectable for many years after recovery from acute HBV infection. HbeAg positive results usually indicate the presence of active HBV replication and high infectivity in HBV carriers and chronic hepatitis individuals. A negative HBeAg result indicates no Viral replication. Anti-Hbe positive results indicate inactivity of the virus and low infectivity. Hepatitis B DNA (HBV DNA) is a marker of viral replication. Higher viral loads correlate with greater infectivity.