We review and summarize published information on diseases caused by Haemophilus influenzae in India and unpublished data from our center covering more than three decades. Since the mid-1950s H. influenzae has been the most common cause of pyogenic meningitis in children admitted to our hospital, accounting for one-third to one-half of cases. Information from other centers in India has been scanty; the lower frequency of isolation of Haemophilus in studies in some centers may be caused by unsatisfactory media and culture methods. The annual numbers of admissions for pyogenic meningitis in our hospital have been quite similar to the numbers of cases of poliomyelitis. Assuming that the similar numbers of children hospitalized with these two diseases indicate similar incidence rates in the community and taking into account the frequency of Haemophilus isolations in pyogenic meningitis, we estimate that there may be as many as 75 to 100 cases of meningitis caused by this organism per year per 100000 children <5 years of age. Although pneumonia caused by H. influenzae has been recognized in a few studies, information is too scanty to attempt the estimation of incidence. Pus-producing infections caused by Haemophilus are rare. Epiglottitis caused by Haemophilus does not seem to occur in India. In recent years we have found that most invasive Haemophilus infections are caused by H. influenzae type b (Hib); other types or untypable strains are infrequent. An increasing prevalence of resistance to chloramphenicol and ampicillin has been recognized in our center and elsewhere. Thus from a hospital perspective, primary prevention by using Hib vaccine seems to be a rational and beneficial intervention. Community-based studies to measure the disease burden of Hib are urgently needed for a more satisfactory assessment of the need for, and cost benefit of, Hib immunization of all infants.