Thermization at 57–68 °C for 10–20 s is the generic description for a range of subpasteurization heat treatments of milk. Thermization markedly reduces the number of spoilage bacteria with minimum collateral heat damage to milk components and it does not cause changes in flavor. Thermization at 62–68 °C for 15 s is practiced widely. The treatment can be conveniently performed in a plate heat exchanger designed for the pasteurization of milk using a standard 15-s holding time. This article focuses on effects of thermization on the quality of milk products (i.e., on) milk components, bacteria, and enzymes. Germination of spores is also addressed including the subsequent inactivation of vegetative bacterial cells by the final heat treatment. Effects of thermization on cheese and liquid-cultured dairy products are also described. The effects of thermization and its positive effects preventing component exchanges in milk, for example, damage of the fat globule membrane caused by the phospholipase of Bacillus cereus, are highlighted.