Over the last 25 yr, cheese production in the United States has more than doubled with most of the increase due to production in the western states. Processing large volumes of milk into cheese has necessitated changes in vat size and design, reliance on computer software, and milk standardization, including use of membrane concentration of milk either at the cheese plant or on the farm. There has been increased interest in specialty cheeses including cheese made from sheep, goat, and organic milks. In addition, membrane processing of whey into various value-added components has become routine. Changes in cheese manufacturing protocols have resulted in a reduction of the manufacturing time and the necessity for consistent and reliable starter activity. Major advances in the genetics of microorganisms have not only resulted in widespread use of fermentation-produced chymosin but also in starter bacteria with improved resistance to bacteriophage infection. Genomics and proteomics have increased the likelihood of the development of nonstarter adjuncts with specific enzymatic activity. Indeed, the use of adjunct microorganisms to produce cheese with a unique flavor profile or to produce cheese with more consistent or better quality flavor has gained almost universal acceptance.