Recent reports indicate that the group B haemolytic streptococcus has now assumed a major role in neonatal septicaemia in the United Kingdom. Of particular concern are the absence of premonitory signs, the fulminating nature of the infection and the high mortality. 31 cases from which this organism was isolated during the first week of life included 5 cases of neonatal septicaemia, 4 of which proved fatal. An attempt was made (a) to identify the group of neonates at greatest risk and (b) to formulate guidelines for early detection and treatment. Study indicates the importance of apnoea as a sign of infection particularly in those infants who are preterm, of low birth weight and asphyxiated. There is need for aggressive bacteriological screening and early administration of antibiotics to prevent the high mortality from group B streptococcal infection.