The aim of this study was to describe the epidemiology, aetiology, and clinical findings in dyskinetic cerebral palsy (CP)in a population-based follow-up study of children born between 1991 and 1998. Age range at ascertainment was 4 to 8 years and prevalence was 0.27 per 1000 live-births. Forty-eight children were examined (27 males, 21 females; mean age 9y, range 5-13y). Thirty-nine had dystonic CP and nine a choreo-athetotic subtype. Primitive reflexes were present in 43 children and spasticity in 33. Gross Motor Function Classification System levels were: Level IV, n= 10 and Level V, n= 28. The rate of learning disability (n= 35) and epilepsy (n= 30) increased with the severity of the motor disability. Thirty-eight children had anarthria. Peri- or neonatal adverse events had been present in 34 of 42 children born at >or=34 weeks' gestation. Motor impairment was most severe in this group. Placental abruption or uterine rupture had occurred in 8 participants and 19 of the 42 near-term/term children required assisted ventilation, compared with 1% and 12% respectively in other CP types. Neuroimaging in 39 children born at >or=34 weeks revealed isolated, late third trimester lesions in 24 and a combination of early and late third trimester lesions in seven. Dyskinetic CP is the dominant type of CP found in term-born, appropriate-for-gestational-age children with severe impairments who have frequently experienced adverse perinatal events.