For many years Branhamella catarrhalis was regarded as a non-pathogenic inhabitant of the respiratory tract. This article outlines the spectrum of B. catarrhalis disease in childhood and the extent of the evidence for a pathogenic role of the organism. B. catarrhalis is a rare etiologic agent in septicemia, meningitis, and other systemic illness in both apparently normal and immunocompromised infants and children. It is an unusual cause of ophthalmia neonatorum, but can be confused with Neisseria gonorrhoeae. Whether or not B. catarrhalis is acquired from the birth canal in these cases has not been established. B. catarrhalis is most common as a respiratory tract pathogen in children, including pneumonia, bacterial tracheitis, sinusitis, and otitis media. Since it is difficult to rigorously document pathogenicity of any bacterium in bronchopulmonary infections in children, it is probable that the spectrum of B. catarrhalis disease is wider than that reported to date. The evidence for pathogenicity in acute otitis media is more extensive than for other infections. Otitis media due to B. catarrhalis is clinically similar to that due to other pathogens. B. catarrhalis can be isolated in pure culture from the middle ear exudate and persists if there is no antibacterial treatment. Gram-negative intracellular and extracellular diplococci can be seen on smears of the inflammatory exudate. There is preliminary evidence that there is an antibody response in B. catarrhalis otitis media. B. catarrhalis has emerged as an important and common pathogen in neonates, infants, and children.