In early December 2003, heavy rains hit southern France, causing flooding in many areas. The breach of the Rhône levees upstream from the town of Arles released several million cubic meters of water, which flooded a vast area, particularly the northern neighborhoods of the city. A large number of people were affected, and more than 7,000 were evacuated. The Bouches-du-Rhône Departmental Directorate of Health and Social Affairs (DDASS) contacted the Southern Interregional Epidemiology Unit (CIRE) to assist in establishing surveillance, with the aim of detecting any health events that could pose a danger to the population and enabling a rapid response. (R.A.)