Issue 19 of Cell Notes, a serial publication of !%Promega Corp.%!, includes an article on the use of the CellTiter-Glo luminescent adenosine triphosphate-based assay to assess cell viability in primary cultures. A discussion on MultiTox-Glo, on MultiTox-Fluor and on CytoTox-Glo cytotoxicity assays for screening applications or for obtaining viability data in multiplex with other cell-based assays also is presented. Other articles cover the use of the psiCheck-2 vector as a biosensor for microRNA activity in cells, the use of the BDNF Emax immunoassay system to understand glutamate excitotoxicity, and the use of two new luminescent assays to study the activity of caspase-2 and caspase-6 in apoptosis. Numerous references, charts and diagrams are provided.