The chemically activated luciferase gene expression (CALUX) in vitro cell bioassay is a bioanalytical tool that is increasingly being used by research and commercial laboratories for the screening and relative quantification of dioxins and dioxin-like compounds in sample extracts. The recombinant cells used in the CALUX bioassay contain a stably transfected AhR-responsive firefly luciferase reporter gene that responds to dioxins and any other chemical(s).