From March 2000 to February 2002, a population-based study of Haemophilus influenzae type b (Hib) meningitis was conducted among children less than five years of age in Hanoi, Vietnam. Children with suspected bacterial meningitis were referred to hospitals and each patient underwent standardized clinical examination and microbiologic testing. In Hanoi, 580 children were evaluated for bacterial meningitis and 23 (4%) had confirmed or probable Hib meningitis. The incidence of all Hib meningitis was 12/100,000 child-years less than five years of age and 26/100,000 child-years less than two years of age. Nationally, an estimated 1,005 children less than five years of age are hospitalized for Hib meningitis and 5,107 are hospitalized for Hib pneumonia. Among children with Hib meningitis, at least 100 will develop severe neurologic sequelae and 40 will die. These data suggest there is a substantial burden of Hib disease in Vietnam. National leaders will be provided with these data to facilitate development of national vaccination policies for children in Vietnam.