Since 1987, surveillance of Legionnaires' disease in France has been based primarily on a mandatory reporting system. Surveillance was strengthened in 1997 through an interactive system for reporting cases of Legionnaires' disease between the National Legionella Reference Center (CNR) and the Institute for Public Health Surveillance (InVS). In 1999, 37 volunteer microbiology departments established the Legionella Observatory in the Île-de-France region, which reports all positive diagnoses to the DDASS and the InVS. At the European level, France actively participates in the EWGLI network. This network, which includes 31 countries, reports to the health authorities of the country concerned any case of Legionnaires' disease in a person who has traveled during the 10 days preceding the onset of the illness, specifying the locations visited. (R.A.)