Thyroid cancer was relatively rare 25–30 years ago, but the number of diagnoses has increased significantly since then. The incidence is highly sensitive to medical and diagnostic practices, which have themselves changed considerably. Enhanced surveillance of thyroid cancer is warranted, as this condition can be caused by exposure to ionizing radiation during childhood. This report presents an update on thyroid cancer surveillance data. It focuses primarily on data from cancer registries (1982–2006) and medical-administrative data (1997–2009). The main findings are as follows: - an increase in incidence has been observed since the beginning of the study period (1982). This increase primarily concerns small papillary cancers; - a slowdown in the growth of incidence is emerging for the most recent years; - in departments covered by a registry, the trends observed are highly varied; - significant spatial heterogeneity in incidence rates is observed; - no change in the incidence of childhood cancers has been observed in the recent period. Changes in medical practices are primarily cited as the explanation for these trends. Quantitative health risk assessments, combined with monitoring of temporal trends and spatial distributions of thyroid cancer, have ruled out a significant impact from Chernobyl fallout in France. Epidemiological surveillance of this cancer must continue to confirm recent trends. (R.A.)