Abstract: The responses to ionizing radiation are complex and are regulated by a number of overlapping molecular pathways.One such stress-signaling pathway involves p53,which regulates the expression of over 100 genes already identified.It is also becoming increasingly apparent that the pattern of stress gene expression has some cell type specificity.It may be possible to exploit these differences in stress gene responsiveness as molecular markers through the use of a combined informatics and functional genomics approach.The techniques of microarray analysis potentially offer the opportunity to monitor changes in gene expression across the entire set of expressed genes in a cell or organism.It again highlights the importance of a cellular context to genotoxic stress responses;it also raises the prospect of expression pro-filing of cell lines,tissues,and tumors.Such profiles may have a predictive value in cancer therapy regimens,or identification of exposures to environmental toxins.