The activities of serum aldolase, amylase and cholinesterase of the maternal and fetal blood were determined in the normal dilivery cases. The following results were obtained. 1) The serum aldolase activities of the maternal and fetal blood are 0.22±0.12 units/1, and 0.46± 0.18 nuit/1. (p<0.01) 2) The serum amylase activities of the maternal and fetal bolld are 233.55±56.22 units/dl, and 67.97±35.51 units/dl. The fetal serum amylase activity is less than one third of maternal one. 3) The serum cholinesterase activitics of the matcrnal and fetal blood are 27.1±1.8, and 23.7±1.3. (p<0.01) The maternal serum cholinesterase activity is higher than fetal one.