The document describes RT2 Profiler PCR Arrays, which allow for pathway-focused gene expression profiling using real-time PCR. The PCR Arrays contain primer sets for 84 relevant genes, plus controls. They have been shown to have high sensitivity, specificity, and reproducibility. The complete system includes optimized primer assays, master mixes, and a first strand synthesis kit. Researchers can use pre-designed arrays focused on biological pathways or diseases, or customize arrays as needed.