Haemophilus influenzae type b (Hib) is an important cause of invasive bacterial disease in children, including meningitis and pneumonia. The introduction of Hib conjugate vaccines into routine vaccination schedules has contributed to a substantial reduction in the burden of Hib-related disease in many developed countries. However, introduction of Hib conjugate vaccines in developing countries has progressed more slowly. We review the worldwide use and effectiveness of Hib conjugate vaccines. At present, 119 countries have programmes for routine Hib immunisation. WHO estimates that in the developed world 92% of the eligible population is vaccinated against Hib; however, average coverage is 42% in developing countries and only 8% in the poorest countries. Africa and southeast Asia have the lowest rates of Hib vaccine introduction. Vaccine costs and debate about the burden of disease are obstacles to the global use of Hib conjugate vaccine. Even with new funding support, there are many ongoing challenges and vaccine use remains suboptimal, particularly in developing countries.