The human serum of about twenty years old men, recently vaccinated has been tested by Laurell's method (Mesnier and Piquet variant). Purified antitetanic equine serum from Pasteur Institute (P.I.) has been taken as reference. With 5 Lf tetanic toxoid from P.I. concentration we can trust in the results until 50 antitetanics I.U. For richer serum, a 10 Lf toxoid concentration must be used. Correspondance between Pasteur Institute serum and gamma TS (human specific immunoglobulins) is indicated. Technics of Laurell, latex and electroimmunodiffusion are compared. The way to obtain plasma pool with higher antitetanic titre than 8 I.U. from poor and rich plasma is mentionned. The highest rate of titre antibody after the first typhoid diphteria tetanic vaccinal injection is observed between the 11th and 21th day.