Surveillance of listeriosis in France is conducted through mandatory reporting (DO) and data from the National Reference Center (CNR) for Listeria at the Pasteur Institute. The CNR participates in the DO system by reporting all Listeria strains isolated from human specimens to the Institute for Public Health Surveillance. The objective of mandatory reporting is to collect information on clinical aspects and the patient’s dietary history in order to identify common factors among patients infected with strains considered identical by the NRC. This makes it possible to trace a potential source of contamination. This article presents the mandatory reporting surveillance system and the results of investigations into alerts in 2001.