Kit contains reagents necessary to perform a competition assay to assess the affinity of test compounds for the human Glucocorticoid Receptor (GR). GR is added to a fluorescent glucocorticoid (Fluormone™GS Red) ligand in the presence of competitor test compounds in microwell plates. The presence of effective competitors prevents the formation of a GS Red/GR complex resulting in a decrease of the polarization value. The shift in polarization value in the presence of test compounds is used to determine relative affinity of test compounds for GR. Designed for room temperature assays, using a coactivator-related Stabilizing Peptide. Alternatively, the assay may be run in the absence of the stabilizing peptide at 4°C, with insignificant change in GR binding characteristics.