Aim: This is the ninth report from the western-Swedish study of the prevalence and origin of cerebral palsy. Methods: A population-based study covering the 88 371 live births in the area in 1995-1998. Birth characteristics, neuroimaging findings and risk factors in children with cerebral palsy were recorded, prevalence was calculated, and aetiology was analysed. Results: The study comprised 170 children with cerebral palsy, i.e. a prevalence of 1.92 per 1000 live births. Excluding eight post-neonatally derived cases, the gestational age-specific prevalences were 77 per 1000 for children born before 28 wk of gestation, 40 for children born at 28-31 wk, 7 for children born at 32-36 wk and 1.1 for children born after 36 wk of gestation. Spastic hemiplegia, diplegia and tetraplegia accounted for 38% , 35% and 6% , respectively, dyskinetic cerebral palsy for 15% , and ataxia for 6% . For the first time, hemiplegia was now most common, due to the decline in preterm diplegia. There was a further increase in full-term dyskinetic cerebral palsy. The origin of cerebral palsy in children born at term was considered to be prenatal in 38% , peri/neonatal in 35% and unclassifiable in 27% , while in children born preterm it was 17% , 49% and 33% , respectively. Conclusion: The decreasing trend from the period 1991-1994 continued, both in children born at term and especially in those born preterm. However, the increase in dyskinetic cerebral palsy in children born at term was a matter of concern. In this group, a perinatal hypoxic ischaemic encephalopathy had been present in 71% . Aim: This is the ninth report from the western-Swedish study of the prevalence and origin of cerebral palsy. Methods: A population-based study covering the 88 371 live births in the area in 1995-1998. Birth characteristics, neuroimaging findings and risk Factors in children with cerebral palsy were recorded, prevalence was calculated, and aetiology was analyzed. Results: The study comprised 170 children with cerebral palsy, ie a prevalence of 1.92 per 1000 live births. Excluding eight post-neonatally derived cases, the gestational age -specific prevalences were 77 per 1000 for children born before 28 wk of gestation, 40 for children born at 28-31 wk, 7 for children born at 32-36 wk and 1.1 for children born after 36 wk of gestation. Spastic hemiplegia, diplegia and the tetraplegia accounted for 38%, 35% and 6%, respectively, dyskinetic cerebral palsy for 15%, and ataxia for 6%. For the first time, hemiplegia was now most common, due to the decline in preterm diplegia. There was a furt her increase in full-term dyskinetic cerebral palsy. The origin of cerebral palsy in children born at term to be prenatal in 38%, peri / neonatal in 35% and unclassifiable in 27%, while in children born preterm it was 17% , 49% and 33% respectively. Conclusion: The decreasing trend from the period 1991-1994 continued, both in children born at term and especially in those born preterm. However, the increase in dyskinetic cerebral palsy in children born at term was a matter of concern. In this group, a perinatal hypoxic ischaemic encephalopathy had been present in 71%.