Group B streptococci (GBS) emerged dramatically in the 1970s as the leading cause of neonatal infection and as an important cause of maternal uterine infection. We review the epidemiology, diagnosis, and therapy of GBS perinatal infection. In 1996, the first national consensus guidelines were released. Since then, there has been a 70% reduction in early-onset neonatal GBS infection, but no decrease in late-onset neonatal GBS disease. In 2002, new national guidelines were released recommending 1) solely a screen-based prevention strategy, 2) a new algorithm for patients with penicillin allergy, and 3) more specific practices in certain clinical scenarios. Yet many clinical issues remain, including implementation of new diagnostic techniques, management of preterm rupture of membranes, use of alternative antibiotic approaches, improvement of compliance, prevention of low birth weight infants, emergence of resistant organisms, and vaccine development.