Patients with chronic hepatitis B virus (HBV) infection have a substantial risk of reactivation and jaundice following the use of immunosuppressant therapy. A single topic conference was convened to discuss the management of HBV patients undergoing chemotherapy for haematological malignancy, liver and renal transplantation and with HIV co-infection. In advance of the meeting a draft guideline was prepared and circulated to a participating expert panel. Presentations and consensus views were obtained on the day of conference to allow pragmatic algorithms to be established on each of these topics. Use of lamivudine prophylaxis for HBV patients undergoing chemotherapy and renal transplantation is strongly supported with good evidence. Patients with HBV cirrhosis who are candidates for transplantation should be started on nucleos(t)ide therapy prior to surgery and, in addition, hepatitis B immune globulin given from the time of transplantation onward. Co-infection with HBV and HIV offers unique challenges. If the patient is a candidate for highly active retroviral therapy then dual nucleos(t)ide analogues which are also active against HBV must be used to prevent immune reconstitution hepatitis. In all these conditions, awareness of possible HBV resistance to therapy must be kept in mind and HBV DNA levels monitored.