From an unselected series of 560 Swedish cases of cerebral palsy, born 1954-1970, various data of etiologic and pathogenetic interest were analyzed in detail. Untraceable and prenatal factors were found to dominate within the group of spastic hemiplegia. Placental dysfunction in small-for-date babies and severe asphyxia were thought to be the two main pathogenetic factors among the patients with spastic tetraplegia. In spite of a significant decrease in the number of low birth weight children within the group of spastic diplegia, this syndrome was still very characteristic for the child born immature. Ataxic diplegic forms were found to have greater pathogenic similarities to spastic diplegia than to simple ataxia. In two-thirds of the children the latter syndrome was characterized by normal pregnancy, delivery and birth weight and an untraceable (genetic?) factor. Dyskinetic syndromes were mostly encountered after perinatal asphyxia.