In order to evaluate the clinical usefulness of Sairei-to in the treatment of toxemia of pregnancy and to study its influence on the waveform of the umbilical arterial blood flow, a standard curve of the pulsatility index (PI) was constructed for 90 patients in their 19th through 41st weeks of normal pregnancy. A dose of 9.0g/day of Sairei-to was then given to 13 patients with edema (mild toxemia) and 3 patients with severe toxemia. These cases were observed for clinical improvement and changes in the PI. The results were as follows: 1) of the 13 patients with mild toxemia, edema improved in 12 cases (92%), along with a decrease in the PI of all of these cases as a result of administration of this Kampo formula, 2) Regarding the 3 patients with severe toxemia, the clinical usefulness of Sairei-to was not clear. In 2 of these cases, arrest of the endodiastolic velocity was observed 6 to 7 days after the start of administration, making it necessary to perform emergency cesarean sections. These findings suggest that in mild toxemia of pregnancy, due to the hydragogue effect of Sairei-to, alleviation of edema and improvement of the insufficiency of placental blood flow, demonstrated by a decrease in PI, could be expected. In severe toxemia, on the other hand, irreversible change had already occurred in the placenta, and consequently, no positive improvement in the insufficiency of placental blood flow could be expected with the administration of Sairei-to. Thus, administration served only to supplement other treatment methods in this group.