Hepatitis B virus (HBV) is a well-known agent of acute and chronic hepatitis, with an estimated 350 million chronic carriers around the world. The presence of HBV DNA in serum is a reliable marker of viral replication and infectivity, and Polymerase Chain Reaction (PCR) is becoming the preferred method for its detection. The aim of the study was to detect serum HBV DNA in chronic hepatitis B surface antigen (HBsAg) carriers using the PCR method to differentiate inactive and active chronic HBV infection in clinical practice. Fifty HBsAg positive serum samples from chronic hepatitis B patients attending Hepatitis Carrier Clinic, Department of Medical Research (DMR) and twenty samples of normal persons with negative HBV serum markers from DMR were collected. HBV DNA was detected by performing PCR with a set of primer pair which was designated to core region of HBV genome. The detection limit of this method was 10-9 ng/ul (102 copies/ml) HBV DNA which was calculated from the serial dilution of HBV genome 1.2 mer (100 ng/ul). HBV DNA was detected in 46 out of 50 (92%) HBsAg positive samples in which HBV DNA level above 105 copies/ml were found in 90% of HBeAg positive and 7% of HBeAg negative samples. All normal samples (100%) were negative for HBV DNA. Four HBsAg positive (8%) showing negative HBV DNA may have low copies number below 102 copies/ml. In these cases, more sensitive methods like nested PCR or real time PCR should be used. As a conclusion, PCR method is a reliable method which can detect HBV DNA in patient's serum simply and differentiate between inactive and active chronic HBV infection which could be widely used in clinical practice.