Over 20 years after the development of the meningococcal A and C vaccines, an effective vaccine against Neisseria meningitidis group B is still lacking. Major obstacles in the development of a B vaccine have been the remarkable capacity of the organism to evade the immune defences of the host and the lack of a predictive animal model. Three group B vaccines based on outer membrane proteins have been, or are currently being, evaluated in field trials. Nevertheless, a number of important questions remain such as the identity of the active components, the degree of efficacy against heterologous group B subtypes, and the duration of protection. In addition, work on a variety of alternative approaches to a group B vaccine is rapidly progressing. Among these are use of chemically modified group B polysaccharide, synthetic or natural lipopolysaccharide epitopes, synthetic peptides corresponding to bactericidal epitopes on the class 1 outer membrane protein, and iron binding proteins. Although each of these approaches has some problems associated with it, the prospects remain good for an effective solution to the group B problem.