Over the past 25 years group B streptococci have become established as one of the main bacterial pathogens of the neonate in Western Europe and the United States. The attack rate of 0.25/1,000 live births found by Mayon White in Great Britain1 appears typical of many European countries. However, in some centers in the United States attack rates can be over 10 times higher.Two types of neonatal group B streptococcus (GBS) diseases exist, “early” and “late” onset. Early onset disease usually presents within the first few days of life. Often the most serious infections are present at birth or seen within a few hours. Early onset disease presents with pneumonia, respiratory distress and shock. Bacteremia is normally present and meningitis may occur. Mortality is high (50% to 75%). The portal of entry is probably the respiratory tract. Infants normally acquire the infecting organism from their mothers. Heavy maternal and infant colonization, prolonged rupture of membranes, prematurity, and obstetric complications are all risk factors.Delayed onset disease, as its name suggests, presents after the first week of life, primarily with bacteremia and meningitis. Mortality is much lower than for the early onset form, but still appreciable for a bacterial infection (14% to 18%). Its epidemiology is uncertain.