Alterations in the p53 gene product appear to be a major factor in human tumorigenesis and may influence the responses of many human tumors to therapy. Much effort has focused on understanding the signals which normally initiate p53 growth-suppressive functions. Though it has been known that DNA damage can induce p53, a recent publication reports data which suggest that p53 can be induced by depletion of ribonucleotide pools, even in the absence of detectable DNA damage(1). These observations provide new ideas about how cells utilize the p53 signal and open up new avenues of investigation for manipulating p53 function.