The risk of cerebral palsy in connection with intrauterine growth retardation has been analysed in a case-control study. The case series comprised 519 children with cerebral palsy born in 1967-1982 in the west health-care region of Sweden and the control series 445 children born during the same years in the same region. The risk of cerebral palsy in small-for-gestational-age infants was significantly increased in term and moderately preterm infants. The highest proportion among infants with cerebral palsy born at term was found in tetraplegia, followed by diplegia and dyskinetic cerebral palsy. It was concluded that small for gestational age on the one hand reflects early prenatal brain damage, and on the other mediates prenatal risk factors compatible with foetal deprivation of supply and also potentiates adverse effects of birth asphyxia and neonatal hypoxia.