Protective immunity to diseases preventable by routine vaccination is lost over time following allogeneic and autologous blood and marrow transplantation. Adoptive transfer of immunity from donors to recipients after allogeneic transplantation is not sufficient to prevent this decline. Systematic reimmunization is necessary at appropriate time intervals following transplantation to re-establish immunity. Response to vaccination depends upon the type of transplant, the source of cells, the immune status of the patient, and the vaccine being used. While inactivated or subunit vaccines are safe in all transplant recipients, live vaccines are generally contraindicated. Reimmunization practices vary widely amongst transplant centers. This comprehensive review summarizes published data on post-transplant vaccination, and based upon these, suggests guidelines which may be used as a framework for development of reimmunization protocols.