Abstract: Specific binding ligands can be detected with an assay which utilizes an immobilized receptor for the ligand, a reporter enzyme, an inhibitor antibody and an anti-inhibitor antibody. Both antibodies are specific for the reporter enzyme. The inhibitor antibody effectively shuts down the activity of the reporter enzyme when it is complexed thereto. The anti-inhibitor antibody binds to the reporter enzyme, does not affect the enzymatic activity, but prevents the binding of the inhibitor enzyme. This assay provides a direct correlation of the target specific binding ligand to the signal generated without the use of separation or wash steps.