**Abstract**

The oxidative status of cells, representing the balance between prooxidants and antioxidants, is involved in their normal physiological functioning, such as signal transduction, proliferation, and differentiation. When the prooxidant activity overrides the antioxidative capacity oxidative stress occurs. Chronic oxidative stress causes cytotoxicity and organ failure. As such, it is believed to play a role in various pathologies, including the hemolytic anemias. In this review, we suggest that red blood cells (RBC), in addition to their primary role as oxygen carriers, function as redox modulators. In the RBC, various systems afford it with antioxidative capacity that, in addition to balancing its own redox state, can provide antioxidative protection to the cellular and intracellular milieus throughout the body. Their vast number, mobility, occurrence throughout the body, and renewability make them good candidates for this function. A decrease in their number (anemia) or function due to oxidative stress may exacerbate the symptoms of many diseases by failing to neutralize oxidative stress. However, correcting anemia, e.g., by repeated RBC transfusions or iron supplementation, may increase the iron load, which, in turn, causes oxidative stress. This situation suggests that the status of both iron and redox should be monitored during treatment, using RBC as bioindicators.

**Keywords:** red blood cells, hemolytic anemia, thalassemia, oxidative stress, flow cytometry
