Without question, one of the main tasks of the red blood cell (RBC) is to deliver oxygen to various tissues and organs in vivo. However, due to the lack of a nucleus and mito-chondria, the RBC is typically not thought to be a determinant in many diseases or abnormal physiological conditions. Recent efforts by many labs world-wide are resulting in a body of evidence, suggesting that the RBC may serve many other roles in vivo besides that of an oxygen carrier. If so, the RBC may eventually emerge as one of the simplest drug targets and diagnostic tools available. Here, molecular evidence is provided, suggesting that the RBC, via its ability (or inability) to maintain proper levels of adenosine triphosphate (ATP) release in the circulation, may be a major factor in vascular regulation. Moreover, due to the RBC’s response to slight modifications in its normal environment, the use of the RBC as an important diagnostic for early prediction of disease onset is discussed.