Maternal immunisation could help to prevent the 2-3 million neonatal and early infant deaths that occur in the developing world each year. Determining the causes of neonatal and early infant deaths in developing countries is difficult as most occur at home. However, it is likely that at least half are due to infections, several of which might be prevented by maternal immunisation. Even in poor countries with few health facilities, a high percentage of pregnant women attend an antenatal clinic at least once during pregnancy. Thus, an effective delivery system for maternal immunisation already exists and, because of the success of maternal tetanus immunisation, this approach to the prevention of serious illness or death in young infants is widely accepted by the general population. However, the high prevalence of HIV and malaria found in pregnant women in some parts of the developing world, especially sub-Saharan Africa, could have an effect on the efficacy of maternal immunisation as both of these infections adversely affect placental function. Nevertheless, the potential of maternal immunisation to prevent early infant deaths in developing countries needs to be fully explored. The incidence of pneumococcal infections is high in many developing countries and about 25% of these infections occur at an age before protection could be anticipated following vaccination with a pneumococcal conjugate vaccine in infancy. Thus, a strong case can be made for a trial of the effectiveness of maternal immunisation with a pneumococcal vaccine in preventing serious illness or death in young infants in developing countries.