The fight against cancer is a government priority that was recently the focus of a five-year national mobilization plan launched by the Head of State in 2003. The epidemiological surveillance of cancers falls within the broader framework of monitoring the health status of the French population, a task entrusted to the French Institute for Public Health Surveillance (InVS). It serves as a tool for decision-makers and is intended to facilitate the monitoring of implemented actions, particularly those under the government’s cancer plan. The current system for monitoring new cancer cases (incidence) relies on registries covering a limited portion of the territory (approximately 15%), with the exception of childhood cancers, which have national coverage. Due to this limited coverage, the system does not allow for a detailed analysis of regional or departmental disparities, nor can it measure the potential impact of exposure to an environmental or occupational carcinogen occurring in an area not covered by a registry. A proposed update to the system, submitted to the Cancer Steering Committee by the InVS, is included among the measures in the Cancer Plan (see box). The national system will be tested for thyroid cancers before being gradually adapted to all cancers warranting national surveillance. (Introduction)