This International Standard give guidelines on the use of screening methods used for the determination of aflatoxin M1 content in milk and milk products, based upon competitive enzyme immunoassays. For legal purposes, positive enzyme immunoassay results require confirmation by an accepted reference method. However, depending on whether the test complies with the specifications given hereafter, enzyme immunoassays can be used for routine quality control, especially when the absence of aflatoxin M1 above the regulatory limit needs to be documented.