Since its success in the European elections of the 17th ]une 84, the National Front of J.M. Le Pen represents today the extreme right which had disappeared as a political force, if not as a way of thinking in France. With 10,95 % of the votes cast, the National Front becomes a political force which must be taken into account, especially when by-elections take place. This ultra-nationalist and populist party focuses the political debate almost exclusively on insecurity and immigration problems but also develops the traditional themes of the extreme right (France's moral and spiritual decline, the struggle against communist subversion... ). The National Front's electorale has poor sociological caracteristics and largely overlaps the traditional extreme-right. The disenchantment of a part of the electorate of the left, the drifting to the right of an important fraction of the electorate, the rising of xenophobia and racism are the principal causes for the relative success of J.M. Le Pen.