Cheese production on a modern scale depends largely on reliable starters which are required to produce uniform acidity during long working hours, be consistent from day to day, and able to work in changeable media for a variety of products under different techniques. Sufficient starters are available, selected to ensure that they have these qualities, but care in handling from day to day, and during the scaling up in quantity, is the most important factor in the practical world of cheesemaking. Some of the main reasons for poor starter behaviour are set out, and a number of alternative systems for maintaining their performance. Care begins in the laboratory, and attention to detail at this stage must be followed by the same vigilance during bulk starter production. One of the most effective methods of achieving overall reliability is described.