summary Erythrocyte transfusion is essential in conditions of large blood loss, of inadequate bone marrow production and of increased erythrocyte breakdown. The structural and biochemical changes that erythrocytes go through during storage, probably associated with the disappearance of up to 30% of the erythrocytes within 24 h after transfusion, are likely to contribute to the transfusion side effects: iron overload, erythrocyte adhesion to the endothelial surface with proinflammatory consequences, autoantibody formation, endothelial damage by released erythrocyte constituents, a hampered microcirculation and oxygen delivery. In vivo, senescent erythrocytes are marked for removal by binding of autologous immunoglobulin G to ageing antigens, which arise by changes in the conformation of the membrane domain of band 3. Also, vesicle formation has been described as an integral part of the erythrocyte ageing process. Comparable changes occur during erythrocyte storage. This review describes the current state of knowledge of the mechanism of erythrocyte ageing in vivo, ageing-related changes occurring during erythrocyte storage in blood bank conditions and their possible relation with the transfusion side effects. In view of the key position of band 3 in the maintenance of erythrocyte structure and function, elucidation of the pathways that control posttranslational modification of band 3 during storage may lead to new approaches towards maintaining ATP concentration and cellular integrity. This review concludes with the challenge to further explore the underlying processes of erythrocyte ageing in order to provide physiologically relevant tools for assessing and predicting erythrocyte homeostasis in vitro and in vivo and thereby to contribute to the development of rational transfusion protocols for various patient categories.