As stored blood ages intraerythrocytic energy sources are depleted resulting in reduced structural integrity of the membrane. Thus, stored red blood cells (RBCs) become less deformable and more fragile as they age. This fragility leads to release of cell‐free hemoglobin (Hb) and formation of microparticles, submicron Hb‐containing vesicles. Upon transfusion, it is likely that additional hemolysis and microparticle formation occurs due to breakdown of fragile RBCs. Release of cell‐free Hb and microparticles leads to increased consumption of nitric oxide (NO), an important signaling molecule that modulates blood flow, and may promote inflammation. Stored blood may also be deficient in recently discovered blood NO synthase activity. We hypothesize that these factors play a potential role in the blood storage lesion.