We aimed to study the rates and trends over time of children with cerebral palsy (CP) of post-neonatal origin (arising more than 28 days after birth, and before the age of 25 months), to examine their aetiology and associated significant risk factors, and to compare them with other CP cases. Children with post-neonatal CP born 1976-90 were identified from a European database and seven registers were included (Surveillance of Cerebral Palsy in Europe collaboration). Using a previously published classification it was possible to allocate an aetiology to 99% of cases. The prevalence rate of post-neonatal CP was 1.26 per 10 000 live births and a significant decrease was observed over the period 1976-90 (P = 0.011). Infection accounted for 50%, vascular episodes for 20% and head injury for 18% of the cases. Although there has been little change in the profile of underlying causes in this period, within the infection group, a significant downward trend was observed for Reye's syndrome (P < 0.001) and non-central nervous system (non-CNS) infection (P = 0.004), but not for meningitis/encephalitis. There was evidence of some increased risk of post-neonatal CP among children with low birthweight (<2500 g) (P < 0.001). Overall children with CP of post-neonatal origin showed a more severe functional pattern than non-post-neonatal CP children. In order to ascertain the impact of public health and other preventive measures aimed at reducing the frequency of brain injury in the first 2 years after birth, it is necessary to continue to monitor the frequency and characteristics of children with post-neonatal CP into the 1990s.