Multilayer films of polyelectrolytes can be prepared by sequential immersion of a charged silica surface into cationic and anionic polyelectrolyte solutions. The formation of such films was investigated using second harmonic generation (SHG), yielding real time information about the in situ adsorption process of each layer within the multilayer film. The SHG results indicate the existence of a fast process (<10 s) that can be ascribed to the initial polymer adsorption to the surface, followed by a slower relaxation due to a change in polyelectrolyte conformation at the surface. The time scale for the reconfiguration varies with the polyelectrolyte.