Haemophilus influenzae type b (Hib) conjugate vaccines were licensed for routine use in the United States in December 1987. We compared national trends in deaths and hospitalization from H influenzae meningitis among children5 years old before and after Hib conjugate vaccine licensure.H influenzae meningitis mortality rates were calculated using data from the 1980 through 1991 computerized national mortality files. Hospitalization rates from H influenzae meningitis were calculated using data from the 1980 through 1991 National Hospital Discharge Surveys. Trends in H influenzae mortality and hospitalization from 1980 through 1887 were compared with trends from 1988 through 1991. Trends for Streptococcus pneumoniae and Neisseria meningitidis meningitis were also examined.From 1980 through 1987, mortality from H influenzae meningitis decreased an average of 8.5% each year, compared with a 48% annual decrease from 1988 through 1991 (P.001 for difference in trends). H influenzae meningitis hospitalization rates increased 1% each year from 1980 through 1987, and decreased an average of 34% each year from 1988 through 1991. There was no significant difference in mortality or hospitalization trends for S pneumoniae or N meningitidis meningitis during the two periods. Among infants, H influenzae meningitis mortality decreased an average of 8% per year from 1980 through 1987 and 43% per year from 1988 through 1991. One- to four-year-old children had similar average annual declines, 8% and 58% for the two periods. Although there were regional differences in the absolute mortality rates, all regions of the country had similar trends in meningitis mortality.Among US children5 years old, we found substantial decreases in deaths and hospitalization from H influenzae meningitis, but not S pneumoniae or N meningitidis meningitis, in the years after Hib conjugate vaccine licensure. These results suggest that the declines in H influenzae meningitis were due primarily to the use of Hib conjugate vaccines.