A safe and effective malaria vaccine will greatly facilitate efforts to control the global spread of malaria. This paper discusses the conceptual framework for developing malaria vaccines and some of the difficulties that the various approaches face. It emphasizes the role of pre-erythrocytic malaria vaccines, which are designed to protect against malaria infection, rather than simply prevent clinical disease. It describes recent encouraging results in human subjects with the RTS,S vaccine, a promising pre-erythrocytic malaria vaccine candidate.