In response to an ongoing scarlet fever outbreak among children and adults at a vacation center in the Hautes-Alpes region, located in the town of Marignane (Bouches-du-Rhône), and the occurrence of secondary cases in Marignane, an epidemiological investigation was initiated to describe the outbreak, guide management measures, and detect complications. Between January 16, 2007, and March 30, 2007, 94 cases were identified (78 children; 16 adults), 43 of which were laboratory-confirmed. At the center, 40 cases occurred during three consecutive stays. In Marignane (n=54), 41 cases were grouped into clusters defined by their family or school contacts. The seven strains isolated at the center were from the same clone. Of the four clones found in Marignane, one was identical to that of the center. No complications were identified. This was an outbreak of exceptional magnitude, though it is not possible to conclude that all cases shared a common origin. The outbreak affected the center and then schools in Marignane, also affecting adults. Aside from antibiotic treatment of the cases, the outbreak ceased at the center following antibiotic prophylaxis for permanent staff, followed by the center’s seasonal closure; in Marignane, it ceased through active communication with stakeholders and the closure of schools for the school break. The occurrence of this outbreak highlights the importance of having a protocol in place for managing clusters of scarlet fever cases in closed communities. (R.A.)