Recently attention in liposome preparation technology has been focused on the preparation of liposomes with a large number of bilayers. These liposomes offer the possibility to encapsulate large amounts of hydrophobic drugs. All methods used to prepare these vesicles are modifications of the method used to produce reversephase evaporation vesicles (REV), as described first by Szoka and Papahadjopoulos (1978). The names for these multi-layered vesicles are: stable plurilamellar vesicles (SPLV), multilayered REV (MLV-REV) and multilamellar vesicles. In order to avoid confusion we will refer to the vesicles prepared by Bangham et al. as multilamellar vesicles (MLV) and to those multilayered vesicles prepared by emulsion techniques as REV-MLV. Gruner et al. compared the physical characteristics of MLV and SPLV. They found that these vesicles had different properties for stability, entrapment efficiency and biological effects, even if they were made from the same materials and appeared quite similar in the electron microscope.