The incidence of clinically significant birth asphyxia was assessed over a 4-year period in a busy teaching hospital maternity hospital. The overall incidence was 6.0 per 1000 live-born deliveries of whom 2.1 per 1000 showed severely abnormal features including seizures or coma. There was a marked seasonal distribution (more common in winter than summer months) and intrauterine growth retardation occurred in 25% of asphyxiated infants. Only 1.6% of these infants were large for gestation age. There is some evidence that the incidence of this condition has not changed over a 10-year period.