Chapter 4 explores reactions to the Provençal plague in Spain with a focus on the port city of Cádiz. It examines the centralization of disaster management during the reign of Philip V, as well as the 1720 plague’s long-term influence on Spain’s public health policy. What emerges in this chapter is an understanding of how Spanish authorities exploited the epidemic by ignoring the terms of treaties and tightening control over its borders, people, and commercial activities. Ultimately, they hoped to reap the advantages of excluding their primary competitors, France and Great Britain, from the hypercompetitive arena of Atlantic commerce. When official news of the plague in Marseilles reached Madrid, the Spanish Crown introduced regulations and supervisory committees that sought to extend the state’s control over commercial activities, both domestic and international, and that meant to exclude its greatest competitors from its commercial market. In the end, much of the new centralized system for disease prevention in Spain followed from reactions to the plague in Provence and remained into the following century, resulting in major changes in the management of both public health and customs inspections.