Streptococcus agalactiae (group B streptococcus) is an important cause of disease in infants, pregnant women, the elderly and immunosuppressed adults. An effective vaccine is likely to prevent the majority of infant disease (both early and late onset), to avoid the limitations of intrapartum antibiotic prophylaxis and to be cost effective. A number of candidates, including capsular conjugate vaccines, have the potential to be successful vaccines. Phase II human studies with capsular conjugate vaccines have been completed successfully. Issues yet to be resolved include the safety and acceptability of vaccination during pregnancy, the durability of vaccine-derived immunity and the regulatory issues required for licensure.