Abstract: The invention relates to an activating composition for the electroless plating of non-conductive surfaces, in particular electronic printed circuit boards.The composition contains a metal complex in which the ligand consists of a quaternary nitrogen compound, especially a compound in which nitrogen forms part of a heterocyclic system and is quaternarized with a radical comprising an acid residue carrying a negative charge, for example a sulphonated group.The invention also concerns a method for the electroless plating involving the use of such composition, preceded by a preliminary treatment of the substrate and followed by the reduction of activating metal.The activating composition according to the invention allows to fix firmly the activator metal to the substrate.