The Haemophilus influenzae type b (Hib) disease burden among children <5 years old in 4 Pacific island countries (PICs) was estimated. The incidence of confirmed Hib meningitis was calculated using the numbers of culture-confirmed isolates. In addition, the World Health Organization (WHO) Hib Rapid Assessment Tool (RAT) was used to estimate the true Hib meningitis incidence and the number of Hib meningitis and pneumonia cases, as well as the number of deaths due to Hib meningitis and pneumonia. The Hib meningitis annual incidence in 3 PICs was 70-84 cases per 100,000 children <5 years old. For PICs, the RAT is likely to overestimate the Hib pneumonia burden, as it assumes a 5 : 1 ratio of Hib pneumonia to Hib meningitis. The true ratio is likely to be 1 : 1. The high Hib disease burden and the relative cost-effectiveness of Hib vaccine make the introduction of Hib vaccine a good investment for PICs, costing US1000 dollars-US10,000 dollars for each death prevented--a number that ignores savings from reductions in the cost of treatment.