Introduction: Hepatitis B virus reactivation (HBVr) is an important complication of immunosuppressive drug therapy. It can occur with active or resolved hepatitis B virus (HBV) infection with a clinical spectrum that ranges from mild elevations in liver tests to fulminant hepatic failure. HBV reactivation is defined as an abrupt increase in serum HBV DNA and alanine transaminase (ALT) levels in a patient with resolved or inactive HBV infection. Study aimed to determine the hepatitis B virus carrier state in patients receiving chemotherapy and determine the incidence of reactivation of chronic carrier HBsAg positive patients who underwent chemotherapy. Material and methods: Patients who were found to be positive for HBs antigen positive were evaluated for further serological markers of HBV to rule out active infection or chronic active infection. Then patients were included in the study and were investigated with prechemo investigations necessary for the chemotherapy schedule. Patients were treated with chemotherapy as per the study protocols. Results: Among the 60 patients only 43 patients had met the eligibility criteria for the study and included in the study. Those 17 patients who do not met the criteria for the study 11 patients presented with jaundice and 3 patients had chronic renal disease and 2 patients had congestive cardiac failure and not included in the study. One patient had rheumatoid arthritis and already on steroids and excluded. Among the 11 patients with jaundice 8 patients were diagnosed as hepatocellular carcinoma and 2 were carcinoma stomach with liver secondaries and one with carcinoma pancreas with liver secondaries. Conclusion: To conclude that the overall incidence of chronic HBs antigen carrier state is about 3.35%. The incidence of reactivation of Hepatitis B virus in chronic HBs antigen patients receiving chemotherapy is 21% as we concluded from the study.