Abstract: p53,acting as a tumour suppressor gene,regulates the system of cell cycle and apoptosis when cells confront a variety of stress including DNA damage responding to ionizing radiation,nucleotide depletion,hypoxia or oncogene activation. In this article,the role and targets of p53 during cell cycle and apoptosis are reviewed. On the basis of it,we question factors of the decision to undergo growth arrest versus apoptosis in response to p53 expression.