Slaughterhouses were among the oldest institutions classified as “dangerous” to public health. Since the nineteenth century, they were subject to standardization, which consisted in alerting butchers to, and preparing them for, sanitary discipline. The article examines this process and the tension it generated by analyzing Parisian slaughterhouses and the municipal slaughterhouse of Saint-Maixent-l’Ecole from 1865 to 1950. The sanitary concerns differed between the capital and the little provincial towns and the municipality had to cope by taking sanitary measures with its own means and control staff. At the local level, the standardization of the activity was imposed by force, often worked out in litigations between veterinarians, policemen and butchers. The new sanitary order was the result of a power struggle. As a result of these conflicts, the acceptance of norms imposed by an exterior authority took quite some time. Clashes actually showed the concrete meaning of the evolution of sanitary morals.