Abstract: The invention relates to a palladium colloid solution, which, in addition to a palladium compound, a protective colloid for stabilizing the colloid and a reducing agent, additionally contains noble metals from the group rhodium, iridium and platinum. The solution can be used to treat electrically non-conductive substrate surfaces, particularly in order to metallize the substrate surfaces directly and electrolytically. By means of this method, the nonconductive areas of the holes in printed circuit boards can be directly electrolytically metallized.