This study examines the efficiency of Doppler flow velocity waveform analysis in the evaluation of the postdate pregnancy. Seventy women whose pregnancies were at or beyond 41 weeks' gestation were assessed by calculating the systolic/diastolic ratios from umbilical and uteroplacental arteries. Waveform ratios from pregnancies associated with fetal compromise and abnormal neonatal outcome were similar to those from pregnancies in which the outcome was normal. These findings indicate that the pathophysiology of placental insufficiency in postdate pregnancies differs from that observed in cases of fetal growth retardation at earlier gestational ages. Doppler flow velocity waveform analysis is unlikely to be of benefit in the routine assessment of the postdate pregnancy.