Hemolysis is a problem associated with a variety of red cell pathologies and physiologies not limited to the transfusion of cells. Various pathways lead to the observed outcomes when a hemolytic event occurs. Each event, and the pathway it follows, is based on characteristics of the red cell, the location in which the hemolysis occurs, and the interaction of the immune system. The severity of an event can be predicted with the knowledge of how these 3 factors interface. Although not all hemolytic events are alike, similarities may exist when the pathways overlap.