For milk and dairy products complete freedom from pathogens is the only accept able standard. To achieve this, pasteurisation or some other form of heat treatment is necessary, adequate precautions being taken to prevent subsequent reinfection of the milk. Physical checks of plant coupled with the use of the phosphatase test, rather than bacteriological methods, serve to ensure the bactericidal efficiency of heat treatment processes and the safety of milk supplies. Bacteriological standards are desirable also to ensure milk which will keep sweet until it is utilized. For this purpose a keeping quality of twenty-four hours after delivery to the consumer may be considered a satisfactory minimum standard. At present, different modifications of the methylene blue test are in use officially for raw and pasteurised milk. In general, compliance with the standards imposed ensures a satisfactory keeping quality, but there is much to be said for a common test and standard for all milk sampled during distribution to the consumer. Direct measurement of keeping quality, using clot-on-boiling to determine the end-point, deserves serious consideration as a method for routine control purposes. For milk to be used for processing or manufacture, a rapid test to be applied to all milk as received is the first consideration. The I0-minute reszaurin test, despite its limitations, is now in general use for this purpose. In addition, however, it is desirable to carry out tests on samples from all producers at intervals, in order to maintain their interest in milk quality and to encourage improvement where necessary. There are no official bacteriological standards for dairy products. There is, in fact, little call for such standards, although manufacturers must, in their own interest, maintain strict bacteriological control over the quality of the raw milk and manufac turing processes. Failure to do so may lead to faults in the products which seriously impair their marketable value or make them entirely unsuitable for human consumption.