Immunogenic compositions containing phospholipid adjuvants, including microparticle and emulsion compositions. According to one aspect of the invention, an immunogenic microparticle composition is provided that comprises: water a polymer microparticle comprising a biodegradable polymer, e.g., a polymer selected from a poly(a-hydroxy acid), a polyhydroxy butyric acid, a polycaprolactone, a polyorthoester, a polyanhydride, and a polycyanoacrylate an antigen absorbed to the microparticle and a phospholipid compound, e.g., a synthetic phospholipid compound comprising: (i) one or more phosphoryl groups independently selected from a phosphate group and a phosphodiester group (ii) a plurality of linear alkane groups. According to another aspect of the invention an immunogenic emulsion composition is provided that comprises: water a metabolizable oil an emulsifying agent an antigen and a phospholipid compound, e.g., a synthetic phospholipid compound like that above. The emulsion composition is an oil-in-water emulsion having oil and aqueous phases, in which the oil phase is in the form of oil droplets, substantially all of which are less than 1 micron in diameter.
