Competitive binding assays are a type of ligand binding assay, used to study the relative affinity of different molecules to the same enzyme or receptor. During this process, a labeled ligand is put into competition with a test ligand for the same receptor, and binding activity between the two is measured. These assays are particularly useful in agonist or antagonist screening, where a molecule’s potential to outcompete a well-defined labeled tool molecule for the same receptor is researched.