The purpose of this study is to: 1) determine the prevalence of Group B streptococcal colonization in newborn infants, their mothers, and hospital personnel attending them, 2) to determine whether serotype prevalence is the same in the above groups, 3) to determine whether infants (not colonized from their mothers) become colonized nosocomially and if so to identify the source/s and mode/s of transmission, 4) to determine disease attack rates in infants of colonized and non-colonized mothers, 5) to determine whether serotype III has characteristics which enhance its disease production (ability to persist, invasiveness). Infant-mother pairs and attendant personnel will be cultured from appropriate sites (at significant times). The Group B isolates will be serotyped. If there is concordance in the three groups as to serotype but the infant colonization rate is significantly higher by the time of discharge, or if there is lack of concordance, studies will be conducted to identify the reservoir/s, and modes of transmission. Surveillance studies will be conducted. Infants with Group B streptococcal disease will be studied as will their mothers and fathers. The attack rate of the specific serotypes will be determined in relationship to colonization rate.