A prospective targeted drug delivery system was prepared by the introduction of complementary and protective moieties at the external surfaces of liposomes. Thus recognition between hydrogenated phosphatidylcholine-cholesterol-based liposomes was achieved by the interaction of the complementary phosphate and guanidinium groups incorporated in separate liposomes while polyethylene glycol chains (PEG) protected both liposomes from environmental factors. In general, protective coating of liposomes in the range of 5% molar incorporation exerted an inhibitory effect on their recognition but it also permitted effective interaction between complementary liposomes.