Intrauterine growth retardation continues to be one of the major problems in obstetrics and still greatly contributes to perinatal mortality and morbidity. This paper reviews the role of Doppler ultrasonography in the antenatal assessment of fetuses with intrauterine growth retardation. Recent developments in this field are described with particular emphasis on the pathophysiologic background of the hemodynamic modification of fetuses with intrauterine growth retardation. Doppler ultrasonography allows the prediction of the development of intrauterine growth retardation in selected populations and the identification among a population of small-for-gestational-age fetuses, those really at risk of unfavorable outcome. Finally, the modifications occurring after the establishment of the growth retardation with the progression of fetal deterioration are described in an attempt to clarify the natural history of this condition. To this end, the longitudinal changes of Doppler indices of placental vessels, fetal arterial vessels, fetal heart, and venous circulation are described, and their complex interrelationship is analyzed. The knowledge of these mechanisms may be useful in deciding the timing of delivery.