The mandatory reporting (MR) of mesotheliomas was established at the request of the Ministry of Health. It is included in the 2009–2013 Cancer Plan. It aims to address two objectives that complement those of the National Surveillance Program for Pleural Mesotheliomas in 23 departments: 1) strengthening epidemiological surveillance of mesotheliomas at all anatomical sites (pleura, peritoneum) throughout France, both metropolitan and overseas; 2) to improve knowledge of cases linked to non-occupational exposures, particularly among women, individuals under 50 years of age, and for non-pleural mesotheliomas (environmental exposure survey). A pilot phase took place in the first half of 2011 in six regions (Aquitaine, Île-de-France, Provence-Alpes-Côte d’Azur, Auvergne, Lorraine, Midi-Pyrénées). It revealed varying situations across regions. Its results and recommendations for the system’s rollout, validated by the Steering Committee and the High Council for Public Health, are presented. The outlook for the DO is described. This system should enable the regular production of surveillance indicators at the national level and for each region, as well as information on the environmental origins of cases. However, achieving the objectives requires the system to be comprehensive and capable of being linked to a complementary collection of information on environmental exposures. (R.A.)