Ionizing radiation has proved to be most valuable in clinical diagnosis and radiotherapy. And also it is used very common in industries especially such as industrial radiography, atomic energy plant, inspectoring by gamma-ray, etc. However, inadvertent exposure to relatively high doses of ionizing radiation is capable of injuring and killing cells. The lungs, because of their rich vascularization, are vulnerable to radiation injury. It is now known that IL-6 is a pleiotrophic cytokine produced by various cells that regulates the immune reponses, acute phage reactions. We performed the immunohistochemical staining of IL-6 on radiation induced lung injury by duration, to clarify the role of IL-6 in tissue damage. IL-6 was strongly expressed in early phase of radiation from alveolar macrophages and damaged endothelial cells. These findings not only have important implications for increasing our understanding of mechanisms of radiation lung injury but they also have an impact on strategies for diagnosis and therapy of radiation damage.