Between 1924 and about 1970, many indigenous enzymes were identified in milk. These were important as indicators of the adequate pasteurisation of milk (alkaline phosphatase, gamma-glutamyl transferase) or of mastitis (N-acetylglucosaminidase, acid phosphatase) and some were considered to be important for the stability of milk (superoxidase dismutase, sulphydryl oxidase). Human and equine milk both contain a very high level of lysozyme, which is considered to have a significant protective effect on the neonate. Progress on the isolation and characterisation of these seven enzymes first isolated in the period 1925-1970, as well as ribonuclease, aldolase and glutathione peroxidase, from the milk of the cow and other species and their significance in milk and dairy products is reviewed in this article. (c) 2005 Elsevier Ltd. All rights reserved.