Transparency, through its multiple applications by the european judge, has become a general principle of european law. Its legal basis resound its purview, imperative and suppletive, its personnal et material scope, as well as its progressive extension and its restriction to the vertical relationships developed between contracting authorities and economic operators. Transparency is attached directly to potential bidders fundamental freedoms whose its provides legal protection. It is attached indirectly to the principle of free competition by the elimination of private barriers to the free movement of economic activities. Thus, in the service of an immediate finality, transparency guarantees access to public procurements and, in the service of a mediate finality, it protects the market structures of public procurement. The general principle of transparency gives then rise to contracts of public order (contrats relevant de la commande publique) which take over public contracts. Instrument of integration and structural element of the internal market, this new generation of contracts materialize access to public order (commande publique), that constitutes a sector of economic activity as part of the internal market.