In France, as in other industrialized countries, the annual incidence of typhoid fever has become very low (0.15 per 100,000 in metropolitan France); on average, 80 cases of typhoid fever are reported annually under mandatory reporting (DO), and more than 80% of these occur upon return from a trip to a country where typhoid fever is endemic. During October 2003, 5 cases of typhoid fever with no history of travel to endemic countries were reported among residents of the Île-de-France region. Given the rarity of indigenous infections with Salmonella enterica serotype Typhi (S. Typhi) in France, and the clustering of cases over time and geographically, a common source of contamination was suspected, and an investigation coordinated by the French Institute for Public Health Surveillance (InVS) was launched to identify the source and implement appropriate control and prevention measures. (R.A.)