The paper considers the classification, composition and growth properties of starter cultures and the significance of bacteriophage and inhibitor effects. The requirements for starter culture are examined and tables given summarizing the features of growth and acid production in milk. The importance of flavour characteristics and curd maturation is discussed, the effects of bacteriophage on cheesemaking studied, and the inhibitory substances present in milk analysed. The use of starter cultures and the selection of the most effective type ‐ single, multiple or mixed strain ‐ used in the production of hard cheese is asses