In November 2004, six cases of hepatitis A that occurred over a two-week period (five students from a preschool and elementary school and one parent) were reported to the Departmental Directorate of Health and Social Affairs (DDASS) of Puy-de-Dôme. The temporal distribution of cases suggested a single exposure to a common source of infection. Information about the disease and its prevention was quickly provided to families, and hygiene measures were implemented at the school. An epidemiological and environmental investigation was conducted to characterize the outbreak, determine the modes of transmission, identify the source, and adapt control measures. In addition, to document viral transmission within the school and among families, saliva tests were performed. This is the first time this method has been used in France to investigate a community-based hepatitis A outbreak and document viral transmission. (Introduction)