ABSTRACT.A retrospective epidemiological study of invasive Haemophilus influenzae type b infections among children in Denmark 1985 and 1986 was carried out and 226 cases were identified. Of these 93% occurred in patients younger than five, corresponding to an annual incidence of 40 cases per 100 000 children aged 0‐4 years, 68% occurred in patients younger than two years of age, and 6% in patients younger than six months. The annual incidences of meningitis and epiglottitis were 27 and 8 cases, respectively, per 100000 children aged 0‐4 years. Of the 156 cases with meningitis four patients died and seven had severe neurological sequelae. Only 67% of the cases of meningitis had been notif