This joint report by the IPSN and the InVS addresses the following topics in turn: an overview of the current state of knowledge regarding both the health consequences of the Chernobyl accident in the most exposed countries and the risk factors for thyroid cancer; a review of the main systems contributing to the epidemiological surveillance of effects that may result from exposure to ionizing radiation in France, as well as a presentation of current knowledge on thyroid cancers in France; a calculation of the risks of thyroid cancer potentially linked to fallout from the Chernobyl accident in France; based on the results of this calculation, a discussion of the relevance and feasibility of epidemiological approaches that could be considered to address the questions raised by authorities and the public regarding the health consequences of the Chernobyl accident in France.