ONE-Glo™ + Tox Assay is designed to improve analysis of reporter gene expression in the context of cell health. The assay combines luciferase chemistry with a cell viability marker in a two-step, addition-only process, to enable measurement of cell viability and gene expression in a single well of a plate, negating the need to run parallel assays. By analyzing reporter activity in relation to cell viability, false results due to toxicity or changes in cell number can be uncovered. Ideally suited for high- and ultrahigh-throughput applications, the volumes of each assay component can be scaled to meet throughput needs and is amenable to automation up to 1,536-well format.