Gajewski JL et al. - Decisions concerning blood transfusions during any of these times may compromise the outcome of an otherwise successful transplant. Years after an HPC transplantation, and even during clinical remission, recipients may continue to be immunosuppressed and may have critically important, special transfusion requirements. Without a thorough understanding of these special requirements, provision of compatible blood components may be delayed and often urgent transfusion needs prohibit appropriate consultation with the patient's transplant specialist. To optimize the relevance of issues and communication between clinical hematologists, transplant physicians, and transfusion medicine physicians, the data and opinions presented in this review are organized by sequence of patient presentation, namely: pre-, peri-, and posttransplantation.