The developmental course of the quantitative aspects of early spontaneous motility was studied longitudinally in fourteen intrauterine growth-retarded infants, with a birth weight below the 5th percentile, in relation to perinatal variables, brain ultrasound findings and neurological outcome. Quantitative motility was studied during the preterm period until term age, from 1 h videotape recordings, using Prechtl's classification of different spontaneous movement patterns. Comparison to a low-risk reference group, consisting of preterm, appropriate-for-gestational age infants, showed that significant differences were inconsistent and obviously by chance, with the possible exception of a decreased rate of startles from the 2nd to the 6th postnatal weeks. A trend of increasing duration of GMs was present with increasing postnatal age. There were hardly any correlations between perinatal variables and quantitative motility, and if present the correlations were weak. Such correlations were found between the reduction of heart-rate variability on cardiotocography and the rate of startles and twitches during the first week and furthermore between the neonatal blood glucose level and the rate of isolated arm movements and total motility during the first week. This study demonstrates that intrauterine growth retardation has little or no influence on the quantitative aspects of spontaneous motility postnatally during the preterm period.