The Authors carried out a research work on problems relating to technical aspects to the tetanus immunity tests. Some interesting conclusions have been reached: - Purified and diluted tetanus toxin is best preserved at - 20 degrees C, in pH 7.4 physiological salt solution added with 1% peptone. - Vaccination in small laboratory animals must be done injecting adsorbed anatoxin by a microsyringe, in order to avoid dilution of the original compound. - Protection test using low, i.v. toxin doses is more reliable than serological tests in assessing the acquired resistance level in immuno-prophylaxed animals. - Passive haemagglutination test is much more sensitive when done with turkey instead of sheep red blood cells.