Many reports of changes in serum protein and fibrin in pregnancy have been published, but a study of the data indicates that the results are not uniform. The majority of the reports indicate that there is a decrease in serum protein and an increase in fibrin. Serial determinations of these substances on the same women throughout pregnancy and the puerperium should definitely demonstrate the direction and degree of change. Furthermore, the determination of the plasma volume on these same patients should make it possible to determine the total amount of serum protein and fibrin, the amounts per kilogram and the variations in total amount in each. Thus, the question of changes in protein in pregnancy would be settled, and some information as to the cause of the physiologic edema of pregnancy and of edema in general might be obtained. In table 1 are listed some of the published data on