The California Mastitis Test (CMT, also known as the California Milk Test) is a simple indicator of the Somatic Cell Count (SCC) of milk. It works by using a reagent which disrupts the cell membrane of somatic cells present in the milk sample; the DNA in those cells to reacting with the test reagent. It is a simple but very useful technique for detecting subclinical mastitis on-farm, providing an immediate result and can be used by any member of farm staff.