The authors make a comparative study of tetanus ímmunization in a group cf children using fluid toxoid containing 20 Lf/c33 and alum precipitated toxoid ccntaining 2 Lf/cm3. The shedule was 3 doses at 21 days interval, using 1 ml fluid toxoid in the first group; 0,5 ml fluid toxoid in the 2nd. one and 1 ml alum precipitated toxoid in the 3 rd. ore. Antitoxins were measured in blood ou tíhe 7 th. and 21 st. days after each toxoid injection. Protective leveis were obtained in all cases after 3rd. dose of both toxoids. When using alum precipitated toxoid the authors noticed that protective levels were reached as early as after the 2nd. dose. With fluid toxoid a 3rd. dose was necessary to reach protective leveis in all cases. Anticoxin liters measured after 3rd. dose did not. demonstrate significative differences between levels obtained with 2 Lf of precipitated toxoid and when 20 Lf of fluid toxeid. Lower titers, obtained when 10 Lf of fluid toxoid was used. Serious side-effects were not observed with any toxoid, though pain was referred at the injection stie with precipitated toxoid.