Hemoglobin-based oxygen carriers (HBOCs) are thought to have an adverse risk:benefit profile when compared to that of transfusing stored red blood cells (RBCs). However, there are clinical circumstances when RBC transfusion is not an option (e.g., patient refusal, unavailability owing to issues of compatibility or remote location). For these circumstances assessment of the risks of an HBOC should be compared to the risks of untransfused acute anemia. In this article we compare the risk of allowing a patient with severe anemia to have a further small decrease in hemoglobin (Hb) concentration to the risk of infusing an HBOC. We conclude that at Hb concentrations less than 6 g/dL, the risk of a further decrease in Hb concentration greatly exceeds the risk of HBOC infusion. Thus, we suggest that there may be a place for use of HBOCs when RBC transfusion is not an option.