Invasive Haemophilus influenzae type b (HIB) infections occurring from 1985 to 1987 in children younger than 16 years of age living in the state of Victoria were reviewed. There were 547 cases which fulfilled the case definition, including 231 cases of meningitis, 219 of epiglottitis and 97 other infections; 14 (2.6%) children died, 8 with meningitis, 5 with epiglottitis and 1 with pneumonia. Ninety-five percent of cases occurred in children younger than 5 years of age, in whom the case attack rate was 58.5/100,000/annum. Nearly two-thirds of cases (46% of meningitis; 91% of epiglottitis; 45% of other infections) occurred in children more than 18 months of age (the age at which vaccine is presently given in the United States). Compared with the United States, the case attack rate for HIB disease in Victoria is lower, the mean age of affected children higher and the proportion with epiglottitis is greater. However, the incidence, age distribution and clinical manifestations of HIB disease in Victoria are similar to those described in Scandinavia before the successful introduction of vaccines. Effective conjugate vaccines against HIB disease are now available and the majority of cases are preventable (depending on the immunization schedule used). These data suggest that immunization of Victorian children against HIB infection should be cost-effective.