A scintillation proximity assay for peroxisome proliferator-activated receptor gamma ligand binding domain is described, Scintillation proximity offers an equilibrium method for detecting ligands that is both cost effective and fully automatable. The method described here is the first reported scintillation proximity assay for a peroxisome proliferator-activated receptor. The design of this system is generic in nature, allowing it to be adapted for other ligand binding proteins. (C) 1998 Academic Press.