Cationic liposomes are being utilized for the delivery of DNA into mammalian cells both in vitro and in vivo. In this report, we describe a rapid, simple injection method for the preparation of cationic liposomes that requires no special equipment. We demonstrate that, using this injection method, liposomes prepared with a commercially available cationic lipid (dimethyldioctadecylammonium bromide, DDAB) or a synthetic cationic cholesterol derivative, along with a neutral lipid (dioleoyl-L-alpha-phosphatidylethanolamine, DOPE), effectively transfect a variety of cell lines in vitro. The transfection activity of liposomes prepared by this method was comparable to that obtained with liposomes prepared by the standard evaporation/sonication procedure and to that of a commercial reagent, Lipofectamine.