The GloMax® 96 Microplate Luminometer in combination with the Beta-Glo® Assay System provides a reliable, homogeneous method to quantitate ß-galactosidase expression in mammalian cells. The Beta-Glo® Assay generates a bright, glow-type signal that remains stable for more than 4 hours. The prolonged luminescence allows for batch processing of multiple plates. The Beta-Glo® Assay System couples the ß-galactosidase cleavage of 6-O-ßgalactopyranosyl-luciferin with the firefly luciferase reaction to generate light. The amount of light produced is proportional to the amount of ß-galactosidase present.