Red blood cell (RBC) transfusions should usually be given only to restore or maintain oxygen delivery to vital organs and tissues. Medical history has clearly documented the importance of blood transfusion in saving lives threatened by acute haemorrhage or severe anaemia. The availability of blood products has facilitated many surgical and medical advances, allowing the support of patients who could not have previously survived invasive therapies. Consequently, the use of blood products has increased steadily over the past half century. However, recent years have seen much greater emphasis on the consequences and costs of transfusion, leading to widespread attempts to restrict blood product use. Balancing the risks and benefits of transfusion has becoming increasingly complex; while restricting transfusion reduces unwanted effects and cost, the thresholds at which the risks of poor oxygen carriage outweigh these are not always clear. Children have different physiology and pathology than adults and many aspects of transfusion practice are poorly researched in the young. This article discusses the most recent evidence available from adult and paediatric research to guide clinical RBC transfusion practice in acute paediatrics. It also discusses the current provision of RBC components for children.