In November 1997, a resident of the town of Gaillon (Eure) reported to the Eure Department of Social Affairs (DDASS) that a family member had been diagnosed with leukemia and expressed concern after learning that other people in her local area had also been diagnosed with the disease. Local general practitioners raised the same concerns. Furthermore, the DDASS had received complaints from the local population regarding environmental degradation, complaints that implicated nearby chemical plants. In 1998, an investigation conducted by the DDASS in collaboration with general practitioners, the town’s medical testing laboratory, and regional hospitals concluded "there appears to be an excess incidence of leukemia (all types combined) in the geographical area comprising the municipality of Gaillon and the surrounding municipalities within a 5-kilometer radius, during the period January 1994–December 1997." In a letter dated July 16, 1998, the Prefecture of Eure requested the National Public Health Network, now the Institute for Health Surveillance, to “confirm or refute this excess of leukemia cases.” The objective of this study is to confirm or refute the existence of an excess incidence of leukemia over a specific period in the suspected area. If this excess is confirmed, a descriptive analysis of the cases will be conducted to identify potential exposures or common risk factors. Concurrently, to provide an indicator of trends in overall cancer risk as well as an indicator of trends in leukemia risk within the study area, a study of all-cancer and leukemia-specific mortality was conducted. Indeed, given the inconsistent quality of national incidence data, the availability of more standardized mortality data—both contemporary and from periods prior to the study period—justifies the use of these mortality data in the risk assessment.