We have developed an assay where the potency of retinoids in retinoic acid receptor (RAR) mediated transcriptional activation can be rapidly evaluated. In this assay hRAR-alpha, hRAR-beta and hRAR-gamma were expressed in CV-1 cells together with a reporter gene containing a retinoic acid responsive element (TRE3-tk-CAT). Concentrations required to obtain half-maximum induction (ED50) of CAT-activity were determined for several retinoids, e.g., all-trans-retinoic acid (RA), 13-cis-retinoic acid (13-cis-RA), arotinoid acid (TTNPB) and m-carboxy-arotinoid acid (m-carboxy-TTNPB, an inactive arotinoid analog). The ED50 values for RA decreased in the order of RAR-alpha (24 nM) greater than RAR-beta (4.0 nM) greater than RAR-gamma (1.3 nM), while the ED50 values for TTNPB and 13-cis-RA decreased in the order of RAR-alpha (6.5 nM, 190 nM) greater than RAR-gamma (2.3 nM, 140 nM) greater than RAR-beta (0.6 nM, 43 nM), respectively. No significant inductions were obtained when cells were treated with m-carboxy-TTNPB, even at 10 microM concentrations. The fold induction of CAT-activity for all compounds tested decreased in the order of RAR-alpha greater than RAR-beta greater than RAR-gamma.