The incidence and case fatality of certain neonatal conditions reported in 692 liveborn infants of birthweights 2000g or less born in South East London in 1970, 1971 and 1973 are presented. 210 (30.3 per cent) died in the neonatal period: respiratory disease and cerebral haemorrhage were the leading causes of death. 482 (69.7 per cent) survived. In these infants, jaundice, respiratory disease and biochemical disorders were the most frequently reported conditions. Because of the numerical importance of the respiratory distress syndrome, both as a single and as an associated diagnosis, a special study was made of predisposing factors. Gestational age, sex, condition of the infant assessed after birth, temperature of the infant on admission for care, and caesarean section were all shown to be independently associated with the incidence of respiratory distress. This confirms the views that the incidence could be reduced if particular attention were paid to the maintenance of body temperature, especially in those infants at risk by reason of the other factors identified.