The AA. have determined the antibodies against tetanus toxin of 739 young people that in 1968 underwent the first vaccination (passive haemagglutination test). 570 subjects (77.13%) entirely immunized and other 129 partially immunized turned out. Whereas the antibodies level of many examined subjects after fifteen years from vaccination was protective, the AA. suggest as correct a vaccination schedule with a dose every ten years to preserve the immunity.