The heat stability of milk has been the subject of a considerable amount of research for about a century. This research has been aimed mainly at understanding the effects of compositional and processing factors on heat stability and elucidating the mechanisms of protein coagulation. This paper provides an overview of the factors that influence the pH dependence of the heat stability of normal and concentrated milks. The principal heat‐induced changes in the milk system that contribute to coagulation are discussed. Current knowledge of the mechanisms of heat coagulation in normal and concentrated milks is also reviewed.