Today, the efficiency of weapons of mass destruction (WMD) non-proliferation regimes is compromised. The attacks on September 11th, 2001, have given more credit to the ghost of the terrorist menace using WMD, at the moment when the frontier between pacific and military uses of nuclear, bacteriological and chemical technologies is increasingly blurred. These attacks are invoked by the Bush administration to justify the questioning of arms control agreements and the adoption of a fight strategy against the more aggressive proliferation (National Security Strategy). Thus, the United States are the architects of the Security Initiative against Proliferation (SIP), a “functional coalition” devoted to counter-proliferation and destined to prevent WMD traffic. Besides raising a certain number of legal problems, SIP complements, as well as complicates, the reinforcement measures of the AIEA measures and exportations control by providers groups. In the fight against proliferation, approach discrepancies oppose the Americans against Europeans. The latter privilege diplomacy and multilateralism over military means to solve proliferation crises (North Korea and Iran). The fight against non-proliferation suffers from a major handicap: it deals with the manifestations and symptoms, not structural causes, of proliferation. The situations of insecurity and regional instability are often at the source of WMD programs, notably in the Middle-East and in Southern Asia. The assessed inevitable erosion of non-proliferation regimes is also due in great part to the absence of a nuclear disarmament process, which is the logical and legitimate counterpart of the fight against proliferation, as the NPT specifies. – Summary AFRI-2004