[en] Since 20 years, the French Institute of Nuclear Protection and Safety (IPSN) works for the reinforcement of the efficiency of the actions against nuclear proliferation. This dossier takes stock of the means and action developed by the IPSN in this domain: nuclear and chemical proliferation: towards a reinforced mastery of risks (status of proliferation during the last 10 years, the aim of the international and national controls, the role of IPSN); nuclear proliferation: the technical control means of the IPSN (inspection, containment/surveillance of nuclear materials (PLUM and FUNE apparatuses), the cooperation between the IPSN and the Kurchatov institute (Russia)); the action of the IPSN in the application of international controls: example of chemistry (conventions, negotiations and expertise, inspections); appendixes: nuclear materials (declaration and permission thresholds), the different steps of the nuclear weapons non-proliferation policy. (J.S.)