This chapter reviews the application of stable isotope ratio measurements to verify the authenticity of dairy products such as milk and cheese using a conventional batch approach. It presents an alternative using a predictive model to reduce the data burden and, hence lower some of the barriers to those wishing to use isotope ratio analysis as an authentication tool for dairy products. A high-profile international case was the addition of melamine to milk powder, which was later incorporated into infant formula. The major constituents of milk are water, lactose, protein, and fat, which typically comprise 87", 4.6", 3.3" and 4.0" of the total milk composition, respectively. Conventional stable isotopes methods have, however, proved unable to distinguish the origin of adulterated dairy products once they are incorporated into mixtures. The importance of milk in the human diet and especially its use as an ingredient in infant formula makes it a target for deliberate contamination for pecuniary gain.