OBJECTIVE: The purpose of this work was to study risk factors and neuroimaging characteristics of cerebral palsy in term and near-term infants. PATIENTS AND METHODS: Among a cohort of 334,339 infants > or = 36 weeks' gestation born at Kaiser Permanente Medical Care Program in northern California in 1991-2003, we identified infants with cerebral palsy and obtained clinical data from electronic and medical charts. Risk factors for cerebral palsy among infants with different brain abnormalities were compared using polytomous logistic regression. RESULTS: Of 377 infants with cerebral palsy (prevalence: 1.1 per 1000), 273 (72\%) received a head computed tomography or MRI. Abnormalities included focal arterial infarction (22\%), brain malformation (14\%), and periventricular white matter abnormalities (12\%). Independent risk factors for cerebral palsy were maternal age > 35, black race, and intrauterine growth restriction. Intrauterine growth restriction was more strongly associated with periventricular white matter injury than with other neuroimaging findings. Nighttime delivery was associated with cerebral palsy accompanied by generalized brain atrophy but not with cerebral palsy accompanied by other brain lesions. CONCLUSIONS: Cerebral palsy is a heterogeneous syndrome with focal arterial infarction and brain malformation representing the most common neuroimaging abnormalities in term and near-term infants. Risk factors for cerebral palsy differ depending on the type of underlying brain abnormality.