A cell line derived from human lung cancer (AOI) was employed in the present study. A panel of cytokines were quantified by ELISA technique following cellular exposure to X-irradiation. Tremendous increase in the levels of both IL-1 alpha and IL-6 were observed, GM-CSF was also detected. A comparison of time kinetics of IL-1 alpha and IL-6 production was made with that of cell cycle progression which was determined by FCM BrdU/DNA bivariate analysis. No cell cycle specific changes were found. The biological implication of radiation-induced cytokine production was discussed.