The rising incidence of thyroid cancer in France and the hypothesis of a link to the Chernobyl accident led the InVS to establish a multidisciplinary commission tasked with assessing the epidemiological situation regarding this cancer. Successive reports from this commission highlight a geographic distribution of thyroid cancers in France that is not consistent with a "Chernobyl effect." It is likely that the increase in incidence is largely due to advances in the diagnosis of thyroid disorders, which allow for the incidental discovery of tumors that were previously undetected.