In France, the mining and milling of uranium ore and the disposal of uranium mill tailings involved nearly 200 sites of very different nature. Being in charge of both the review of some remediation reports and the routine monitoring of the environment provides IRSN with selective data on most sites. The data collected by IRSN as well as those available from other data sources often remain incomplete therefore preventing IRSN from presenting a global view or answering some specific questions. In order to overcome this difficulty, it was decided, under the aegis of the Ministry of Ecology and Sustainable Development, that IRSN should develop a program of investigations organized in two parts: Part 1, called “State of knowledge" is aimed at assessing the amount of information available and at consolidating it into a user-friendly computerized database. The main goal is to identify the occurrence of significant enhanced radiological levels in the environment and to detect any lack of information concerning the various sites. This paper gives an overview of the information already collected. Part 2, called “specific studies" is aimed at fixing the gaps in the database by implementing new investigations on specific sites. It could lead to improvements in networks for the monitoring of radioactivity in the environment.