In a longitudinal, blinded study design the predictive value of Doppler velocimetry for the development of an abnormal fetal heart rate trace was assessed in 42 cases of intrauterine growth retardation. Doppler velocity waveform recordings were obtained at 2- to 3-day intervals and characterized by the standard deviation score of the pulsatility index in the umbilical artery and internal carotid artery, and the peak systolic and time-averaged velocity in the ascending aorta and pulmonary artery. Twenty-seven patients did not display an abnormal fetal heart rate trace on the day of entry into the study. During follow-up of these patients, the pulsatility index in the umbilical artery and internal carotid artery were the most predictive parameters for the development of an abnormal fetal heart rate trace. The resulting prognostic index was found to have an acceptable discriminative power in the prediction of abnormal fetal heart rate traces as established in a second group of growth-retarded fetuses.