The nationwide DPT vaccine program was started in 1969 for infants under 12 months of age. In order to estimate the tetanus immune status among the general population of various age groups, we measured the serum tetanus antibody level in randomly selected outpatients from Metropolitan Tokyo (n = 211, 6 months-60 years) and Hamamatsu, a city of 510 thousand population (n = 128, 3 years-80 years) between January 1987 and June 1989. Among the 211 subjects from Tokyo, the antibody value exceeding effective level of 0.01 HAU/ml was observed in 102 subjects (48.3%). The antibody positive rate was 90.8% in subjects of 3 to 21 years and was 27.7% in subjects of 22 years or older. The positive rate was significantly higher in subjects of 21 years or younger (p less than 0.005). Among 128 subjects from Hamamatsu, 60 (46.1%) had a positive antibody and the antibody positive rare was 96.9% in subjects of 3 to 21 years and was 29.5% in subjects of 21 years or younger (p less than 0.005). The above findings indicate that our DPT vaccination program has been functioning well for the last 20 years and that the immunized population is adequately protected against tetanus.