The pulsatility index (PI) of the umbilical arteries was measured in 40 hypertensive pregnancies. Doppler-velocimetric data were kept unknown to the clinical staff. An abnormal PI was found in 79% of cases in which an abnormal fetal growth in utero had been diagnosed by ultrasonographic measurements. Serial PI findings showed worsening figures in most of the cases with an abnormal fetal growth, irrespective of the last absolute value. Amniotic fluid estimation and PI data were significantly correlated. PI values were markedly abnormal in fetuses with non-reactive heart-rate tracings. A high sensitivity and an optimal specificity were found for umbilical PI versus the diagnosis of fetal growth retardation made by the coexistence of different biophysical criteria. However, false normal results may occur. 62% of the newborns weighed below the 5th percentile. The sensitivity of abnormal PI values to detect these light fetuses resulted to be only 67%. However the prevalence of neonatal morbidity in fetuses with abnormal PI values was 74%, while morbidity occurred only in 14% of cases with normal PI values. In hypertensive pregnancies, this simple velocimetric parameter proved to correlate with abnormal biophysical monitoring and complicated neonatal outcomes.