Firefly luciferase is a widely used reporter for studying gene function and regulation in mammalian cells or tissues as they lack endogenous luciferase activity. Light production from the reaction however, causes build-up of toxic adenyl-oxyluciferin at the enzyme surface that shortens half-life of light emission (flash-type) and makes batch-analysis or high-throughput screening (HTS) impossible. The Steady-Luc™ HTS assay is a proprietary formulation that extends the signal half-life to ~3h (steady-glow) by preventing adenyl-oxyluciferin build-up. The high-sensitivity, homogeneous, glow-type reporter gene assay allows high-throughput quantification of luciferase expression in mammalian cells in microplates. The lyophilized format allows room temperature shipping and -20°C storage. It provides excellent performance at an economical priced to compared to other brands.