The evaluation of the antitetanus immunity in human sera is of primary importance for the carrying out of an adequate prophylaxis and treatment of tetanus. Tetan Test is a diagnostic kit for the titration of the antitetanus antibodies, by means of the passive hemagglutination technique. Tetan Test is examined under the point of view of the preparation techniques and the process and final controls which warrant the quality and the standardization of the product itself. The stability of Tetan Test, after storage at the temperatures: 67 degrees C, 52 degrees C, 37 degrees C, 22 degrees C is evaluated. The excellent results obtained allow the use of the product also in hot climates, in developing countries, where the storage at the advised temperatures is not possible.