Continuous-wave and pulsed Doppler ultrasound measurements of blood flow velocity waveforms of both uterine and umbilical arteries were performed on 85 patients to assess the correlation between these two measurement techniques. Peak systolic to end-diastolic (S/D) ratios measured by continuous-wave devices were not statistically different (P> .05) from those measured by a pulsed Doppler device. The S/D ratios of the umbilical artery measured by each device showed a strong correlation, whether measured by one observer (r=0.93) or two observers (r=0.89). Uterine artery ratios showed a weaker, although still significant, correlation (r=0.57). Pulsed Doppler is not routinely necessary for the identification and measurement of umbilical and uterine artery S/D ratios.