The interaction of DNA with salt-free tetradecyltrimethylammonium hydroxide and lauric acid lamellar vesicles with positive charges was investigated to probe potential applications of vesicles in DNA transfection. The aggregation morphology of the vesicles changes greatly with the addition of DNA due to the dissociation of anionic surfactants, as indicated by H-1 nuclear magnetic resonance, and the expelled surfactant molecules self-assemble into micelles at high concentrations of DNA. Salt-free cationic and anionic (catanionic) vesicles have a much higher binding saturation point with DNA at R = 2.3 (the ratio of DNA to the excess positive charge in vesicles) than formerly reported salt-containing systems, implying high transfection efficiency. DNA retains its native stretched state during the interaction process. This very interesting result shows that catanionic vesicles could help transport undisturbed and extended DNA molecules into the target cells, which is of great importance in gene delivery, nanomedicine field, and controlling the formation of certain morphological aggregates.