Neutral lipids have received up to now a little attention as genetic material carriers, despite some valuable features, such as the,, absence of toxicity and the high stability in serum of their complexes with DNA. We have prepared two quaternary complexes of DNA and mixtures of 1, 2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-hexanoylamine (6PE) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-dodecanoylamine (12PE) with DOPC in aqueous dispersions of bivalent metal cations (PE/DOPC-DNA-M(2+)). The aim was to evaluate the effect of the amide moiety on the transfection efficiency. These complexes form in a self assembled manner, the DNA condensation being promoted by the metal cations. Synchrotron X-ray diffraction analysis was used to determine the structure of the complexes, which exhibit the lamellar symmetry of the L(alpha)(c) phase. The size and surface charge of the complexes have also been measured, and promising results of DNA transfections in vitro have been reported.