To determine whether pregnancy and the gravid uterus have an effect on phleborheographic findings, 48 asymptomatic pregnant patients underwent phleborheography in the second or third trimester or the immediate postpartum period. Their phleborheograms were compared to normal phleborheograms of nonpregnant patients with normal venograms. No difference was detected between the phleborheograms of the two groups. Furthermore, there was no change in the phleborheograms of patients who were tested in the second and third trimesters and also in the immediate postpartum period. The fact that the gravid uterus and pregnancy did not alter the venous wave amplitude and baseline tracing indicated the absence of chronic or acute venous obstruction. The use of a lateral rather than supine position was judged important in obtaining accurate findings. The study suggests that phleborheography can be used to diagnose deep venous thrombosis in pregnant women with the same confidence as in nonpregnant patients.