Newborn infants with "early-onset" disease due to group B beta hemolytic streptococcus were studied over a 40-month period. Clinical presentations included asymptomatic bacteremia, mild transient illness, respiratory distress, meningitis, and overwhelming sepsis. Chronologically, 18 were ill at birth; 10 became ill after a symptom-free period; and four were asymptomatic. Sixty-six percent of the cases weighted less than 2500 grams, and 56% were born to mothers whose amniotic membranes were ruptured for over 20 hours. All 15 of the deaths occurred in low birth weight infants who were criticially ill from birth. A review of 128 consecutive deliveries of infants weighing under 2000 grams revealed 28 cases with prolonged ruptured membranes, and three of these 28 infants developed group B streptococcal infection. The infant of the colonized gravid woman in premature labor or with prolonged ruptured membranes is clearly at risk, and these results suggest that the management of "early-onset" disease should begin prior to delivery.