Tetanus antitoxin was quantitatively measured in 912 pregnant women by indirect hemagglutination test. The mothers who received no dose, one dose and two doses of tetanus toxoid were 64.6%, 10.1% and 25.3% respectively. The percentage of mothers with protective antibodies in the groups receiving none, one, and two doses of tetanus toxoid were 95.4, 100 and 100. The level of protective antibody in the newborn and the magnitude of transfer rate of passive immunity to tetanus depended directly upon the level of tetanus antitoxin in maternal serum. Mothers who had tetanus antitoxin of 1.28 IU/ml or more could transfer protection to almost all of the newborns (97%-100%) irrespective of doses of tetanus toxoid administration. However, mothers who had received two doses of tetanus toxoid during pregnancy not only confer good protection but also transfer a high tetanus antitoxin levels to their newborns.