Abstract: Recently, liposomes as a potential drug-carrier have been studied both in vitro and in vivo. Experiments have shown that the liposomes will be able to become a vehicle for the selective delivery of some drugs into target cells, especially into malignant cells. But after being prepared, liposomes itself which are bilayered phospholipid vesicles are so unstable that it cannot be stored for more than several days.In order to stabilize liposomes, we searched for some stabilizing agents. By means of electronmicroscopic observation and ultrafiltration method we found that liposome solution containing mannitol and polyvinyl sulfate (PVS)seems to be stable at 4℃.Electronmicroscopic picture demonstrated that the liposomes in mannitol—PVS solution showed no obvious morphological changes during 100 days at 4℃. The results of ultrafiltration experiments demonstrated, too, that the liposomes in mannitol—PVS are much more stable than that in normal saline either stored at 4℃ or at low temperature in a mixture of solid CO₂ and acetone.