In France, the fight against cancer is a top public health priority. This involves, in particular, improving the epidemiological surveillance system, which is one of the seventy measures included in the latest cancer plan launched by the government in March 2003. The current system for monitoring cancer incidence relies on registries covering only a limited part of the country, with the exception of the registry for childhood cancers, which has national coverage. Consequently, it cannot meet the demands of public authorities and society regarding the impact of risks—particularly environmental risks—that may arise anywhere in the country. The InVS has proposed an upgrade to the system to the government. It is based on the recommendations of a multidisciplinary working group for the establishment of a national epidemiological surveillance system for thyroid cancers. This system will then be progressively applied and adapted to all cancers warranting national surveillance, particularly those potentially linked to environmental exposure, and in accordance with priorities defined jointly by epidemiologists, researchers, and policymakers. It is based on the development of a partnership for routine surveillance of new cases, initially based on hospital data and health insurance reimbursement data, and subsequently on anatomo-cytopathological (ACP) data. Alerts will be handled locally under the coordination of the Cires. The proposed national system is a multi-source system of anonymized and linked individual data, centralized at the InVS. The goal is to have a unique anonymous identifier for each patient, which would be generated within each data source before the encrypted data is transferred to the InVS, in order to link the different sources and identify duplicates and recurrences. The establishment of this national system is planned to take place within five years. (R.A.).