Blood transfusion is the transfer of blood or blood products into the blood-stream of a patient who has lost blood due to injury, disease or an operation. The amount and type of blood or component transfused depends on the needs of the patient. Transfusions of blood and blood products are routine and are generally safe therapeutic procedures that are rarely associated with adverse reactions. However, it is only in the last hundred or so years that the foundations of these procedures have been established. Similarly, the transplantation of organs and solid tissues from one individual to another to replace diseased or nonfunctional tissue is now well established. However, it is little more than 50 years since the first successful clinical transplant of a kidney in 1954 paved the way for the range of tissue transplants cur-rently available. Advances in the transplantation of bone marrow and stem cells have brought the two fields of transfusion and transplantation closer together.