Among 19,044 children born to mothers with monitored pregnancies and followed medically for at least 5 years, 41 (0.2%) had cerebral palsy that was not the result of a progressive disease or of a neural tube defect. All children without cerebral palsy were entered as controls subjects in the analysis. Significant prenatal or gestational predictors of cerebral palsy were a severe or nonsevere birth defect other than cerebral palsy or its sequelae, low birth weight, low placental weight, abnormal fetal position, and premature separation of the placenta. Maternal antecedents of cerebral palsy were unusually long or unusually short intervals between pregnancies and unusually long menstrual cycles. Perinatal risk factors were delayed crying as a measure of birth asphyxia and abnormal delivery. Children who had seizures within 48 hours of birth were at high risk for the development of cerebral palsy. Seventy-eight percent of children with cerebral palsy did not have birth asphyxia, and the 22% who did had other prenatal risk factors that may have compromised their recovery.