This chapter gives a broad overview of the possible spoilage defects in consumer milk, being either of a microbiological nature (e.g. spore formers and Pseudomonas enzymes) or of a chemical nature (e.g. light-induced oxidation). As these defects can be quite specific for, e.g., pasteurised versus ultra high temperature (UHT) treated milk, a detailed description of the mechanisms of spoilage, the main factors (on farm or industry level) influencing this spoilage, and the methods (including emerging methods on farm or industry level) to prevent spoilage, are discussed for different types of consumer milk. Finally, some future trends and further reading advice are given.