prior to the late 1980s, haemophilus influenzae type b (hib) was the most common cause of meningitis, epiglottitis, and other invasive bacterial infections in young children. the introduction of the conjugate hib vaccines dramatically decreased the incidence of invasive hib disease in young children and is thus recognized as a great public health achievement. since the vaccine's implementation, there have been concerns about capsule switching and serotype replacement, which may allow non-type b h. influenzae to fill the ecological niche previously occupied by hib. recently, reports identifying non-type b serotypes of h. influenzae causing invasive diseases have been published. moreover, there appears to be a large number of indigenous people affected by non-type b h. influenzae. this study examined the incidence of invasive h. influenzae disease in northwestern ontario, canada.