Multilayer films of the complexes between nucleic acids (native DNA, heat denatured DNA, polyuridic acid) and aliphatic amines with C-chain length from 16 to 24 have been obtained by the Langmuir-Blodgett (LB) technique. These films were investigated by small angle X-ray scattering and IR spectroscopy. The main structural features of the films are the aliphatic amine bilayers and lamellarly ordered nucleic acid strands between them. The interlayer distances of the complexes of the aliphatic amine with the nucleic acids were found to be by 7-8 Angstrom greater than those of the aliphatic amines without nucleic acids. IR spectra of the LB films at various relative humidities reveal that the multilayer complex formation is provided by the interaction between PO2- and C=O groups of nucleic acids and NH3+ -groups of aliphatic amines. This means that the native DNA unfolds during the LB films fabrication. On the other hand, IR spectra of LB film of the DNA-dioctadecyldimethylammonium complex show native conformation of DNA molecules in the films. The obtained results are under discussion.