The quality of sheep milk is paramount in controlling the quality of dairy products made from it. We describe the factors affecting the quality of the milk of sheep milked commercially for dairy production, with an emphasis on Australia and New Zealand. Some of these factors, such as the genotype of the sheep, are difficult to control, but others are environmental factors, such as the nutrition and management of the milking flock, and can be manipulated by the farmer to produce high quality milk. To obtain high quality milk, ewes must be milked out regularly and completely, which implies adopting appropriate milking routines and milking equipment. It is also important that the ewes are healthy and receive adequate diets. Physiologically the ewes must be in an appropriate stage of lactation because at the very beginning and at the end of lactation the milk is of poor manufacturing quality, even though it has high fat and protein content. These factors and their influence on milk quality for the processing of milk into dairy products, especially cheese, are described and critically examined.