An increasing number of ionizing radiation (IR)-responsive genes are being reported, and it is now possible to perform a genome-wide analyses of structure of the promoter of IR-responsive genes. Characterization of IR-responsive gene promoters is considered to provide an important insight into the biological defense system against detrimental effects of IR, because such information enables us to discriminate genes involved in cellular IR-response only on the basis of the nucleotide sequence of the promoter. Here we will review the recent research that aimed to reveal the common structure of IR-responsive genes. It was reported that the frequency of initiator (Inr) in IR-responsive genes was higher than that in general genes, and the frequency of GC-box and CCAAT-box was significantly lower than that in general genes by an analysis of 217 IR-responsive human genes that were compiled from microarray databases available in the literature. It was also reported that utilization of the GC-box and the CCAAT-box in IR-responsive genes is correlated with the TATA-box status, that is, GC-box frequency was low in TATA box-containing genes, and CCAAT-box frequency was also low in TATA-less genes. These findings suggest that the regulation mechanism of IR-responsive genes is fundamentally different from that of general genes. No apparent biased use of the core promoter element in association with a specific gene function was observed. Biological significances of the observed difference in utilization of core promoter elements between IR-responsive genes and general genes will be discussed in regard of possible interplay between transcription factors.