Rabies immunosomes are prepared by the anchorage of glycoprotein molecules to preformed liposomes. Virosomes are associations of glycoprotein molecules with viral or non viral lipids. Virosomes can be obtained spontaneously after removal of the detergent used for lipids solubilization. Under the electron microscope immunosomes look like homogenous spherical vesicles (50-60 nm) evenly covered with spikes, although glycoprotein molecule orientation in virosomes is not yet clearly established. In addition, the size of virosomes is very heterogeneous. When glycoprotein molecules are in immunosome form, their accessibility to a lectin (WGA) is identical to that of the purified virus. Under the same conditions with virosomes accessibility is weaker. Protection induced in mice is ten to twenty fold higher with rabies immunosomes than with purified glycoprotein or virosomes. The results presented here and previous reports (10) show that immunosomes have structural and immunogen characteristics closer to those of purified and inactivated virus than does any other form of glycoprotein lipids association.