Prophylactic irradiation of blood and blood components is accepted practice in order to prevent graft-versus-host disease from infused lymphocytes. Irradiation, however, results in increased red cell potassium (K+) loss, along with other possible effects that may affect red cell function and viability. Lipid peroxidation (LP), a process initiated by the production of oxygen free radicals, is increased in red cells in the presence of reactive iron species and various heme moieties. In this report, it is noted that not only is plasma K+ significantly increased following blood irradiation, but LP is also increased compared with paired non-irradiated blood samples. Furthermore, various metal chelators significantly reduce LP in the irradiated samples. These chelators also significantly reduced the rate of cellular K+ loss during the four day 37 degrees C incubation period. This study further suggests that the addition of selected metal chelators may be effective in both irradiated and non-irradiated stored blood by improving the function and viability of transfused erythrocytes.