A quantitative analysis of various fetal activities (mouth, eye and gross body movements) was made in 10 IUGR human fetuses. The aim of the study was to see whether IUGR fetuses move differently to normal fetuses. Each real-time ultrasound recording lasted 1 h and the analysis of various activities was carried out during replay of video recordings by means of a specially designed computer program. The following aspects have been investigated: (1) incidence, duration and interval for each of the fetal activities described; (2) the relationship between incidence, duration and interval for each single activity; (3) the correlations between the different activities. The results were compared with a group of 10 fetuses from normal pregnancies. On quantitative evaluation no clear effects due to uncomplicated IUGR could be detected except for median duration of eye movements, which turned out to be longer in the IUGR group. The evaluation of correlations between the characteristics (incidence, duration and interval) of each activity showed a positive correlation between incidence and duration of mouthing movements in the IUGR group, not found in the normal group. The study of the correlation between different fetal activities has shown an inverse correlation between mouthing and other activities in the normal fetuses, not found in the IUGR group. We conclude that in mildly affected fetuses with no evidence of hypoxia, there are no quantitative differences compared to normal fetuses in terms of the motility studied. The only differences found were in relation to the performance of such activities and they could reflect a dysfunction of the central nervous system resulting from a metabolic disturbance.