The results are reported of a nationwide prospective epidemiological study in Israel whose purpose was to provide a background for decisions regarding the need for Hib conjugate vaccinations. During the two study years, 344 patients < 13 years of age with a positive blood or cerebrospinal fluid culture for Hib were seen in 25 medical centres in which paediatric patients were hospitalized. The overall incidence of Hib disease was 34 per 100,000 persons < 5 years old, an incidence in the range of those reported for western Europe. Similarly, the incidence of meningitis was 18/100,000. During the first year of life, the incidence of Hib was 117/100,000 and 93% of all cases were < or = 24 months old. The age distribution of our patients resembles that of immunologically compromised populations or of persons living in less industrialized areas, but the incidence of disease is similar to that found in western Europe. The data presented justify the widespread use of conjugate Hib vaccines in Israel.