Issue 20 of “Cell Notes,” a serial publication of !%Promega Corp.%!, focuses on drug discovery and screening. The 32-page document includes an article on monitoring viability during gene-directed enzyme prodrug therapy with the CellTiter-Glo assay and human neural progenitor cells, and a discussion on detecting toxicological responses in cells with the bioluminescent GSH-Glo glutathione assay. Other articles address screening traditional Chinese medicines, RNAi knockdown in primary cells, cytochrome P450 activity in rat hepatocytes cultured on a synthetic extracellular matrix, and high-throughput kinase and multiplex cytotoxity assays. Publications that cite the use of Promega reagents and technologies in novel high-throughput screening applications are highlighted.