Researchers in the p53 field have successfully used many high-throughput screening technologies to analyze and characterize p53 -induced gene expression. This chapter will focus on one such technology, the Affymetrix GeneChip�. DNA-Chip technology has grown rapidly over the last several years. The ability to hybridize RNA from a sample to thousands to tens of thousands of known and unknown cDNAs spotted on a microarray chip has led to the explosion of information ranging from macro-global expression pattern changes to micro-gene-specific expression changes. The relative ease of making a nonradioactive probe from either total RNA or mRNA to be hybridized to a GeneChip makes microarray technology highly attractive.