Transfection competent complexes were assembled using a three component system. The constituents of the basic system were plasmid DNA, cationic DNA binding protein (NLS-H1) and anionic liposomes (dioleoyl phosphatidylethanolamine (DOPE) or phosphatidylserine (PS)). In contrast to cationic liposome/DNA binary complexes, all of the DNA in these ternary complexes was sensitive to DNase I degradation and ethidium bromide intercalation. Transmission electron microscopy revealed that these ternary complexes formed unique structures in which the DNA was located either on the outside of individual liposomes or bridging two or more liposomes. This provides evidence that plasmid DNA encapsulation is not essential for transfection competency.