In a geographically-based study, we investigated the risk of cerebral palsy following intrapartum asphyxia at term, and the contribution of intrapartum asphyxia at term to the overall rate of cerebral palsy. We used stringent criteria for identifying intrapartum asphyxia, while recognising that the initial hypoxial insult might have occurred in the antenatal period. In the first part of the investigation, a cohort of 160 term, singleton infants, with a low (< or = 3) 1-minute Apgar score, was followed to the age of 5 years. Six infants in the cohort had presumed intrapartum asphyxia, of whom two died in the neonatal period, three had spastic quadriparesis, profound developmental delay and visual impairment, and one was unimpaired. The frequency of cerebral palsy associated with birth asphyxia was estimated as one in 3700 full-term livebirths. To assess the impact of birth asphyxia on the overall rate of cerebral palsy, all cases of cerebral palsy born in the study period were identified. Of the 30 cases, the three identified in the follow-up study were the only ones whose impairment could be attributed to birth asphyxia in a full-term birth. Birth asphyxia at term therefore was associated with 10% [95% confidence interval (CI) 2.1, 26.5] of all cases of cerebral palsy and with 20% (95% CI 4.3, 48.1) of the 15 cases of cerebral palsy in children born at term.