The transfusion of red blood cell (RBC) concentrates is the main treatment for acute vaso-occlusive symptoms in sickle cell disease (SCD). Units of packed RBCs (pRBCs) must retain optimal characteristics for transfusion throughout the storage period. Transfused RBCs interact with the plasma and the endothelium that lines blood vessels and may be the target of immune-hematologic conflict if the patient produces antibodies against RBCs. Questions remain concerning the benefit-risk balance of RBC transfusions, in particular about the shelf-life of the units.