Multilayers films of nucleic acids (DNA, polyuridylic and polyadenylic acids) and polycations (polyallylamine, polyethylenimine, polylysine and polyarginine) were fabricated by consecutive adsorption of anionic and cationic polyelectrolytes. The nlm growth process was controlled by X-ray reflectivity and UV spectroscopy. The penetration of DNA-specific dye was examined for DNA-polyallylamine self-assembled films.