An ongoing population-based register of cerebral palsy (CP) in the West of Ireland was established in 2002 to calculate the prevalence of CP and to monitor CP epidemiological trends in the area. Children were only included if they were at least 5 years of age; children with postneonatal CP were also included. Eighty-five children were identified, giving an overall prevalence for the period 1990 to 1999 of 1.88 per 1000 neonatal survivors (95% confidence interval 1.5–2.4). Males accounted for 68% (n=51) and females for 32% (n=24) of all cases. Among infants weighing less than 1500g at birth, the rate of CP was 39/1000 neonatal survivors compared with 1.3/1000 for infants weighing more than 2500g. The most common CP subtype was bilateral spastic CP (51%), followed by hemiplegia (32%), dyskinesia (9%), and ataxia (7%). Eighteen per cent of all children were unable to walk, 21% had a sensory impairment, and 56% had an intellectual impairment.