During a 20-month period we studied 175 pregnant women at high risk for hypertensive disorders of pregnancy or intrauterine growth retardation, and 172 patients at low risk, in a prospectively designed cross-sectional trial. Using duplex pulsed wave Doppler ultrasound, we recorded blood velocity waveforms from both main uterine arteries, the uteroplacental arteries in the region of placental implantation and the umbilical artery at 21-24 weeks of gestation. Persistent notches in the main stem uterine arteries and elevated resistance indices of > 0.68 in the uterine arteries and > 0.38 in the uteroplacental arteries were defined as abnormal waveforms. The incidence of proteinuric pregnancy-induced hypertension (PPIH) and intrauterine growth retardation (IUGR) were recorded as main outcome measures. Doppler proved to be more efficient at predicting a complicated pregnancy in those patients who were at high risk: a positive medical history alone was associated with a three-fold greater risk of developing PPIH and/or IUGR. In the high-risk group a single pathological Doppler sign accounted for an additional three- to four-fold increased risk, and the combination of all three pathological signs, a seven-fold additional risk for later disease. In this group PPIH and/or IUGR was found in 58.3%, compared to 8.3% if Doppler results were normal. The criterion for the definition of pathological Doppler results, whether persistent notching, the resistance index (RI) of the main stem uterine artery, or the RI in the arteries of the uteroplacental bed, was of minor importance, as all Doppler parameters were strongly correlated. However, the combination of all parameters was superior to a single parameter, and a bilateral notch was superior to a unilateral notch in terms of minimizing false-positive results. However, Doppler was less powerful in the population at low risk. Here PPIH and/or IUGR was seen in 6.1-6.4% in the group with abnormal Doppler findings compared to 5.2% in pregnancies with normal findings. None of the patients showed bilateral notching. In conclusion, pathological Doppler velocimetry of the uterine and uteroplacental circulation was a powerful predictor of PPIH and/or IUGR in high-risk pregnancies, identifying a group in which 58.3% would suffer from disease later in pregnancy. A combination of several Doppler parameters was superior to a single parameter, although the parameters were strongly correlated with each other.