This issue contains a description of progress toward the development of a vaccine for Hemophilus influenzae, type b.1 The present status of this vaccine and the successive steps that must be taken to determine the safety and efficacy of any such product before it can be recommended for use are outlined, and a description of the antigenic anatomy of H. influenzae is included. Acquaintance with this information should be of value to pediatricians in the not-too-distant future when immunization against this organism may become available. Why should attempts be made to develop a vaccine against H. influenzae? Review of the literature suggests three reasons: the frequency of meningitis due to this organism, the apparent increase in that frequency, and the severity of the disease in spite of current treatment.