The purpose of this work is to obtain lyophilized preparation of tetanus antitoxin, and to study the effect of freeze-drying on the keep­ing quality of the lyophilized products. Six of antitetanic serum (ATS) products were prepared. These products were: liquid ATS with phenol 0.5%, lyophilized ATS with phenol 0.5%, lyophilized antitoxin immuno­globulin (ATI) with phenol 0.5%. liquid ATS with sodium azide 0.2%, lyo­philized ATS with sodium azide 0.2%, lyophilized ATI with 0.2% sodium azide. Saccharose 1% and glycine 2% were used as stabilizer during lyo­philized process. Sterility, safety and potency tests were applied for evaluation of different prepared lyophilized products. The results showed that the lyophilized products were easy re­constituted with distilled water. The products were prepared from MS with sodium azide 0.2%, ATS with phenol 0.5% and their concentrated antitoxin immunoglobulin (ATI) were bacteriology, mycoplasma and fun­gal sterile, potent and safe for injection. This study proved that the lyophilized process of the ATS either lyophilized as it is or lyophilized after concentration of antitoxin immuno­globulin has no effect on the sterility, safety and also has no significant effect on the potency of the freeze-dry products.