The chemokine receptor CCR2 is a G protein-coupled receptor that is activated primarily by the endogenous CC chemokine ligand 2 (CCL2). Many different small-molecule antagonists have been developed to inhibit this receptor, as it is involved in a variety of diseases characterized by chronic inflammation. Unfortunately, all these antagonists lack clinical efficacy, and therefore a better understanding of their mechanism of action is warranted. In this study, we examined the pharmacological properties of smallmolecule CCR2 antagonists in radioligand binding and functional assays. Six structurally different antagonists were selected for this study, all of which displaced the endogenous agonist 125