Liposomes have been widely used as drug delivery systems for many years. However, they are of limited use as delivery systems for subunit vaccines due to their low immunogenicity. Here we examine the effect of incorporating the adjuvant Quil A into liposomes on the type of particles produced, on the ability of the different particles to incorporate antigen and on the ability of the different particles to stimulate murine bone-marrow-derived dendritic cells (DC) and lymphocytes. The incorporation of increasing amounts of Quil A, from 20% to 70% of the total lipid into liposomes, reduces the size of the particles that form in aqueous dispersion and decreases antigen incorporation and uptake by DC. Interestingly, the particles with 20% Quil A were more toxic to cells in culture than the particles containing 70% Quil A, and the 20% particles were also more immunostimulatory.