This article attempts to demonstrate that the idea of clean milk, which goes without saying today, had a long and difficult history in terms of its acceptance. It was necessary first to describe the actual idea of “clean milk”, something which seemed to take several decades. The National Clean Milk Society, which was one of the instigators of this process, was a voluntary organization set up by the wealthy landowner, Wilfred Buckley. It played a major role in convincing the authorities that it was possible to produce milk more hygienically and of a better bacteriological quality, leading in the 1920s to the official drawing up of a quality statute. It was, by contrast, a lot more difficult to convince the farming world of the economic benefits of producing clean milk and what that actually meant in concrete terms. Some progress was made in the 1920s and 30s, but in rural areas and small towns, regulation of milk production was not very advanced ; in some areas, milk would thus remain an unsafe, even dangerous, product, carrying a variety of diseases, into the 1950s.