Chemotherapy drugs, biological medications that are used to treat cancer, may cause hepatic side effects. Patients with pre-existing viral hepatitis may be more susceptible to exacer-bation of their underlying liver disease, and risk of drug-induced hepatotoxicity. We conducted a search on immunosuppression, and its impact on reactivation of viral hepatitis, using the electro-nic medical databases. Before starting chemotherapy, it is recommended to record the past history of liver disease and check for hepatitis B virus (HBV) and hepatitis C virus (HCV) serology. In immunosuppressed patients, radiation toxicity, graft versus host disease, hepatic veno-occlusive disease, acalculous cholecystitis, tumor infiltration, ischemia, other viruses such as CMV and her-pes virus, and systemic infection should also be considered. Transplant recipients with serologic evidence of previous infection with hepatitis B or C, or those who receive organs from a seropo-sitive donor, should have viral load levels monitored before and after transplantation and, may also require treatment. We believe that there is a role for prophylactic use of antiviral treatment in patients at risk for HBV reactivation.