Small unilamellar vesicles associated with plasmid DNA showed maximum association efficiency for a cationic mixture of egg phosphatidylcholine (EPC):1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE):di-1,2-dioleoyl-3-trimethyl ammonium propane (DOTAP) (16:8:1 molar ratio) [65%], followed by neutral lipids EPC:1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE):cholesterol (Chol) (2:2:1 molar ratio) [30%], and a polymerized formulation 1,2-bis(10,12-tricosadiynoyl)sn-glycero-3-phosphocholine (DC8,9PC):DMPE:Chol (2:2:1 molar ratio) [11%]. The hydrophobicity factor (HF) for these formulations followed the trend DC8,9PC:DMPE:CHOL < EPC:DMPE:Chol < EPC:DOPE DOTAP, and DNA association did not alter this trend. Results suggest that the higher the HF value, the more fluid the membrane and the higher the efficiency of DNA association. On the other hand, no differences were observed in cell toxicity with lipids up to 1 mg/ml in VERO cells.