1. Using paper electrophoresis, the normal value of each fraction of serum protein was estimated in 10 nonpregnant normal Taiwanese women. 2. The paper electrophoresis of serum protein in each group of 10 pregnant women in each pregnancy month totalling 90 women, showed a progressive decrease of plasma protein and albumin and an increase of α-and β-globulin as the pregnancy advanced. 3. 11 cases of ectopic gestation, 6 cases of hydatidiform mole, 6 cases of abruptio placentae, 5 cases of eclampsia, 11 cases of preeclampsia and 4 cases of choriocarcinoma were studied in comparison with the normal pregnant women. It was noted that the change of the serum protein was proportional to the severity of toxemia of pregnancy. 4. With paper electrophoresis of serum protein, afibrinoganemia in abruptio placentae cases was easily detected, thus making a great contribution to the diagnosis and treatment of this clinical entity. 5. The figures of paper electrophoresis of the intraabdominal blood in ectopic gestation cases roughly corresponded to those of the peripheral blood of the patients.