For the French population, exposure to radon, along with medical exposure, is the primary source of exposure to ionizing radiation. Radon is a known lung carcinogen for humans: it is classified in Group I by the International Agency for Research on Cancer (IARC). According to available estimates, the estimated number of lung cancers attributable to radon exposure in France is far lower than that caused by tobacco. However, according to a recent European study, approximately 9% of lung cancers in Europe are attributed to radon. Thus, the number of people exposed makes radon a public health issue that requires action, especially since exposure levels can be significantly reduced through often simple measures. Starting in 2002, the French Nuclear Safety Authority (ASN) has been working to implement the new regulatory framework for managing radon-related risks in public spaces. The new system put in place is now fully operational. Furthermore, building on the measures adopted by the Government in June 2004 as part of the National Health and Environment Plan (PNSE), the ASN developed in 2005, in consultation with the Ministry of Urban Planning and Construction, an interministerial action plan for 2005–2008 designed to coordinate the efforts of the various national agencies involved in this field. This plan is organized around three main areas: - developing a new policy for managing radon-related risks in existing housing and new construction; - supporting and monitoring the implementation of regulations for managing radon-related risks in places open to the public; - improving and disseminating knowledge about radon exposure and related risks. (R.A.)