In a retrospective study in Orebro, Sweden 1956-1980, 201 cases of bacterial meningitis in children over the age of 1 month were analysed. The aetiology was Haemophilus influenzae in 123 cases, Neisseria meningitidis in 55 cases and Streptococcus pneumoniae in 19 cases. We registered a significant increase in incidence of H. influenzae meningitis from 5.6 (1956-1965) to 13.0 (1971-1980) per 100,000 children and year (p less than 0.01). The mortality decreased from 19% to 4% during the period studied. This decrease was primarily due to a reduced mortality in hospital later than 12 h after admission. Hearing impairment was the most frequent sequel (10%) and no change in frequency was observed during the 25 years studied. Hearing impairment was registered significantly more often in cases with a late admission to hospital (greater than 48 h) as compared to cases with an earlier admission (p less than 0.001).