We have studied doppler recordings of flow velocity waveform of the umbilical artery in 380 high-risk pregnancies and 160 patients with uncomplicated pregnancies. The results were not used in clinical management. In 24 cases, all in high-risk pregnancies, there was absence of end diastolic flow (AEDF). Four babies died, 22 out of 24 weighted less than the 5th centile for gestation and 20 were delivered by Caesarean Section. With only four exceptions, all fetuses showed other evidence of antenatal fetal compromise, though this was delayed in some cases for up to 24 days. AEDF does not appear to prejudice neonatal outcome. All six babies born weighing 750-999 g survived. In addition, 4 patients continued their pregnancy for 3-6 weeks after the first doppler with AEDF. Only one of the 4 developed other evidence of fetal compromise and two had vaginal deliveries. In our experience, AEDF is found only in abnormal pregnancy, and is a very serious sign of likely fetal compromise. It is an indication for extremely careful surveillance but not necessarily an indication for delivery.