Four cases of cancer believed to have occurred at Bignon School (Mortagne-au-Perche) over a period of less than three school years were reported to the Student Health Promotion Service (SPSFE). The school principal was the source of the report. To take into account the local context and, in particular, the existence of a social demand, the Prefect of Orne requested that Cire Ouest “implement the methodological tools for investigating clusters.” (R.A.)