Issue 16 of “Cell Notes,” a serial publication of Promega Corp., focuses on drug discovery and high-throughput screening, emphasizing the use of in vitro assays to understand in vivo biology. The 32-page document includes articles on the MultiTox-Fluor multiplex cytotoxicity assay, and on in vitro compound profiling in 384- and 1536-well plates using bioluminescent assay systems. It discusses multiplexed viability, cytotoxicity and apoptosis assays for cell-based screening, and the DPPIV-Glo luminescent protease assay, which detects Gly-Pro cleaving activity in serum. Sections also cover timing apoptosis assays and the use of luciferase reporter assays to screen for G-protein-coupled receptor modulators. A kinase assay product flowchart is included.