This article looks at the way enterprise size acts as an important factor (in France and the EC) in the structure of the productive system, based on two principal analyses : the sectoral breakdown and the geographical location of businesses. The strict ranking of enterprises according to their size is also highlighted. The different microeconomic, macroeconomic and even cultural factors which lead to these business classifications are analysed. Finally, the question of the consequences of these elements on the performance of different sized enterprises is studied.Cet article s'intéresse à la façon dont la taille des entreprises apparaît en France et dans la Communauté européenne, comme un important vecteur d'organisation du système producti...