Subjects who had exhibited a strong local reaction after vaccination with tetanus toxoid showed a high serum antitoxin titer. This observation confirms earlier findings published in the United States. Since the falloff rate in tetanus antitoxin, year by year, is no more than 30%, such patients should not receive a new booster injection in the following 10 years unless the risk of tetanus is considered great. When boostering these persons, the dose of tetanus toxoid can be reduced to 1-2 Lf.