The GAL4-UAS system is a powerful technique for studying gene expression and function. It has also been adapted to study nuclear receptor chemical-binding functions. Our PPAR-delta LBD-driven GAL4 reporter HEK 293 stable cell line is a reliable, rapid, and sensitive method for analyzing the intracellular status of NRs upon exposure to drug candidates or other stimuli. These functional assays allow for measurement of receptor activation or inhibition by compounds and can be used to determine compound potency and selectivity.