We have recently introduced a new method of creating ultrathin films based on the electrostatic attraction between opposite charges. Consecutively alternating adsorption of anionic and cationic polyelectrolytes leads to the formation of multilayer assemblies. Here, we extend our concept to the procedure of ultrathin (100–500-Å) film growth with alternation of DNA and poly(allylamine) molecular layers. Multilayer buildup was monitored by small-angle X-ray reflectivity; the step of growth for layer pairs of DNA/poly-(allylamine) was 40 Å. The relationship between this growth mechanism and the process of natural complex formation between DNA and polyamines (spermine, spermidine, etc.) may be of interest.