Fetal heart rate (FHR) variation, general movements (FGM), breathing movements (FBM) and haemodynamics were studied longitudinally in 19 intrauterine growth retarded fetuses, who eventually were delivered by caesarean section (CS) because of fetal distress, in order to determine changes occurring with time. The fetuses were studied for the last 10 days on average before delivery (range 2-14 days). During this period on average eight 1-h FHR records were made and three 1-h movement recordings. The FHR pattern was analyzed numerically; the incidence of FGM and FBM was quantified and expressed as percentage of time. Blood flow velocity waveforms were measured in the umbilical artery (n = 19) and in the internal carotid artery (n = 14). In 14 of 19 fetuses abnormal velocity wave forms were present from the beginning of the study onwards. FHR variation was initially just within or below the norm and fell further during the last 2 days before CS. FGM and FBM fell below the normal range later and in a lower rate of occurrence than FHR variation. FGM showed a more or less consistent fall in time, whereas FBM showed a wide range throughout the period of observation. The poorest outcome occurred in fetuses with reversed end-diastolic velocities and rapid fall in FHR variation. It is concluded that with progressive deterioration of the fetal condition abnormal velocity wave form patterns occur first; FHR variation is reduced subsequently and FGM and FBM are the last to become abnormal. Assessment of fetal activity may be of help in fetuses with a marginally reduced FHR variation, in which prolongation of pregnancy is considered desirable to allow further maturation in utero.