Summary Total body irradiation (TBI) is a well established conditioning regimen for patients who had undergone bone marrow transplantation. TBI not only offers a slightly significant survival advantage over Busulphan-based conditioning regimens but also lower toxicity profile. However the biological process after TBI seems rather different than conventional routine partial body irradiation. Not only the tolerance doses but also time to occurrence of the organ toxicities show a variation. It has been shown that there are alterations in trace element content in kidney after TBI in addition to cytokines and redox-active metal composition of blood. Acute phase proteins also have been shown to rise after irradiation. Considering all these evidences we suggest that TBI changes the blood content of trace elements, acute phase response proteins with probably many other inflammatory proteins and cytokines within the blood and this change in blood content may sensitize the organs to radiation.