The p53 tumor-suppressor gene is mutated in a wide range of human cancers. The ability of p53 to control passage through the cell cycle (in G1 and in G2) and to control apoptosis in response to abnormal proliferative signals and stress, including DNA damage, is considered to be important for its tumor-suppression function. p53 is a transcription factor that binds to DNA in a sequence-specific manner to activate transcription of target genes. In this chapter, we describe the application of differential display to identify p53-regulated genes.