Efforts to develop a meningococcal vaccine that will include coverage against serogroup B disease have largely focused on outer membrane protein antigens. The protection offered by currently licensed outer membrane vesicle (OMV) vaccines is specific to epidemic strains as their immunodominant antigens are highly variable. Many new developmental vaccines use multiple-antigen components to improve coverage, but these are often not very immunogenic without an effective adjuvant. In this article, some proposed mechanisms of adjuvant action are discussed, particularly with respect to use in developmental meningococcal vaccines. Many of these vaccines use OMVs as vaccine components, and the inherent adjuvant properties of these vesicles will also be discussed. As few adjuvants are currently licensed for use in humans, and predicting clinical efficacy from preclinical investigations is difficult, it is likely that OMVs will continue to be used for their adjuvant properties in meningococcal vaccine development in the near future.