This study examined isolates of group B streptococci (GBS) by latex seroagglutination and restriction endonuclease analysis (REA). REA analysis was performed with high- and low-frequency cutting enzymes, and fragments were resolved by linear and pulsed-field gel electrophoresis (PFGE), respectively. GBS isolates were derived from a regional acute-care hospital and a tertiary referral obstetric hospital. The most common serotype isolated at the general hospital was serotype V (42%). A high incidence of this serotype V was associated with wound infections, but there was no predominant REA profile. Serotype III was the most common from the obstetric hospital (41%). The majority of these isolates were associated with neonatal GBS infection and there was a predominant restriction pattern. Analysis of restriction patterns of GBS isolated from individual mother/ baby pairs revealed common patterns. These data extend the evidence for vertical transmission of GBS and clones of serotype III GBS with increased pathogenic potential.