This International Standard gives guidelines for the standardized description of immunoassays or receptor assays for the detection of antimicrobial residues in milk and milk products. It is intended to provide a framework and basis for the evaluation/validation of tests based on the binding of an antimicrobial compound to its specific antibody or to other types of detecting molecules. In addition to immunoassays [e.g. enzyme-immunoassay (EIA) and radio-immunoassay (RIA)], there are several quantitative, semi-quantitative and qualitative test formats based on the binding of antimicrobial compounds to microbial receptors or to receptor proteins. Enzymatic assays and particle-based assays based on receptor proteins are referred to as receptor assays in this International Standard.