An aqueous dispersion of niosomes (non-ionic surfactant vesicles) emulsified in an external oil phase forms the vesicle-in-water-in-oil (v/w/o) system described in this paper. The properties of the surfactant used to form the vesicles, the surfactant or surfactant mixture used to stabilize the emulsion and the nature of the oil phase can be changed to provide systems of different capacities for drug or antigen and different release characteristics. The same nonionic surfactant is used as the principle amphipile to form the niosomes and to stabilize the w/o emulsion, thus promoting stability by decreasing transfer of surfactant between the stabilizing monolayers and the vesicle bilayers. The in vitro release of carboxyfluoroscein and 5-fluorouracil encapsulated within the niosomes of the v/w/o system has been investigated, the nature of the oil phase and surfactant-oil interactions being important in determining the rate of solute release. Initial studies of the system in vivo, as an adjuvant for tetanus toroid, using cottonseed oil as the external oil phase, showed enhanced immunological activity over the free antigen or vesicles.