This review will give a short introduction to the principles of cheesemaking and some definitions of cheese yield, and the characteristics in milk influencing the cheese yield and cheese quality will be discussed. Good quality milk, giving an optimal cheese yield and cheese quality, originate from healthy animals, has good flavour, has been cold stored for a limited amount of time and has a high protein content with the BB genotypes of ß-lactoglobuline and κ-casein (bovine milk). The milk should be low in somatic cell count, as proteases from somatic cells attacks α_S2- and ß- caseins and reduce the cheese yield. The content of free fatty acids should be low, as free fatty acids bind Ca²⁺ and thereby reduce the coagulation properties of the milk, in addition free fatty acids contribute to the development of rancid flavour in cheese. Milk used for cheesemaking must be of good microbiological quality, pathogenic bacteria should be absent, psychotropic bacteria have heat resistant lipases and proteases which may reduce yield, but may also cause undesirable flavours in the ripened cheese. Clostridia spores cause late blowing in cheeses with eyes, but also to cheeses with closed texture these bacteria induce inedible flavours. Antimicrobial agents as antibiotics, detergents etc. must be absent, as the acidification by lactic acid bacteria will be strongly influenced.