The risk of hepatitis B virus (HB) reactivation is high in patients receiving chemotherapy for solid or hematological malignancies which may lead to premature termination of chemotherapy or delay in treatment schedules. The consequences of HBV reactivation range from self-limited conditions to fulminant hepatic failure and death. The following slide-set reviews the pathogenesis, risk factors, diagnosis and management of HBV reactivation in patients undergoing chemotherapy.