A study was carried out in 6 Kecamatans in Yogyakarta. A total of 56 and 163 blood samples were collected from 4—7 month pregnant women and mothers 17—35 years of age. The objectives of this study was to know the immune respons against tetanus after being vaccinated with tetanus toxoid adsorbed during pregnancy (a prospective study) and to know the decrease of the antibody level 1—4 years after vaccination (a retrospective study). Tetanus antitoxin titration was performed by passive haemaglutination (PHA) test. Tetanus toxoid adsorbed used in this study was produced by Biofarma, Bandung. Two immunization doses against tetanus with 1—2 months interval gives 100 % protection to the babies at birth, and at the age of 3 month the babies still have protective titres against tetanus. The percentage of mothers with tetanus protective titres decreased from 80,70 % to 53,57 % with the mean antibody titres decreased from 0.415 HAU/ml to 0.066 HAU/ml after 1—4 years vaccination.