We have developed liposomes which can be easily prepared with inexpensive lipid, have enhanced stability, and can efficiently deliver DNA into the COS-1 cells. Liposome formulations were prepared using cationic materials such as dimethyldioctadecyl ammonium bromide(DDAB), cetyltrimethyl ammonium bromide(CTAB). We investigated the effect of cationic liposome formulations on in vitro DNA transfection. DDAB-containing liposomes showed increased transfection efficiency which was 3.2-fold as much as that by Lipofectin^ⓡ, but CTAB-containing liposomes were inactive in gene transfection. The effect of colipid of DDAB-containing liposome was also investigated. As a colipid, dioleylphosphatidylethanolamine(DOPE) and cholesterol did altered the transfection efficiency of DDAB-containing liposomes. And increased DDAB concentration lowered the transfection efficiency. The optimum amount of liposomal formulation was 10μM for 1㎍ of DNA. In the experiment of stability. DOPE-containing liposomes formulation showed a broad size distribution and separation of two major peaks on a 5th day of preparation, but liposomes containing cholesterol was stable for 10 days. DDAB-containing liposomal DNA delivery system was prepared easily and was stable.