[en] Hepatitis B is a blood-borne viral disease which affects more than 250 million people world-wide, mostly in the third world. The disease can cause fatal liver cancer in adult life, if infected when young. This deals with the laboratory techniques used in the detection of hepatitis B virus of the donor blood. Natural blood transfusion service of Sri Lanka screens the hepatitis B surface antigen using the RIA technique to find out whether the normal healthy donors without a history of hepatitis are infected with hepatitis B virus