There is currently intense research activity aimed at the development of new delivery systems for vaccines. The goal is to identify optimal methods for presenting target antigens to the immune system in a manner that will elicit immune responses appropriate for protection against, or treatment of, a specific disease. Several different approaches to this general goal have been developed, some are empirical and remain poorly understood, others are more rational, being based, for example, on mimicking natural infections in vivo or on targeting particular features of the immune system. This article will review three categories of delivery systems: (i) adjuvants and formulations; (ii) antigen vectors, including live attenuated micro-organisms and synthetic vectors; and (iii) novel devices for vaccine administration. The review will be restricted to late stage developments in the field of human vaccination.