The commercial application of enzymes as a feed additive has a history of less than 20 years. During this period, the feed enzyme industry came into existence and it has gone through several phases of development. The first phase was the use of enzymes to enhance nutrient digestibility, focusing primarily on removing the anti-nutritive effects of non-starch polysaccharides (NSP), such as arabinoxylans and β-glucans, from broiler diets based on viscous grains like wheat, rye, barley or triticale. During the early 1990s, the scope of enzyme application expanded to consider nutrients other than NSP and benefits other than digestibility enhancement. Phytase is a prime example, where not only was it used to increase the utilisation of phtate P, but also to alleviate environmental burdens by reducing P excretion in the excreta. The industry then started to advocate enzyme addition to poultry diets based on non-viscous grains, such as sorghum and corn. Although such a use is not uncommon in some parts of the world, the industry is still in search for highly efficacious enzymes for non-viscous cereal grains. The next phase is the application of enzymes to non-cereal grain components of the diet. These vegetable protein sources are often high in NSP, which are poorly characterised in regard to their molecular structures. Significant progress has been made on characterisation of the NSP in soyabean, but the industry has not been able to produce commercially viable products that consistently improve the digestibility of vegetable protiens. The enzyme industry today is constantly searching for new areas of application. Some recent data demonstrate the role of glycanases (charbohydrate degrading enzymes) as an alternative to in-feed antibiotics. It is possible to produce enzymes tailored for (a) the generation of specific low molecular weight carbohydrates in vivo, which, in turn, produce specific health outcomes in birds; (b) de-activation of anti-nutrients other than NSP and phtate, and (c) degrading of non-conventional feed resources to yield ME. The development of enzyme technology needs to go hand in hand with better characterisation of substrate structures, the gut microflora, and the immune system.