Abstract: Peritoneal exudate collected from mice infected with Toxoplasma gondii was centri-fuged at 15,000 rpm (4℃) for 60 minutes, the supernatant is the soluble antigen (S), The sediment, a mixture of parasites and host's cells, was suspended in distilled water and disrupted by ultrasonication at 330 mA for 5 minutes. After adding equal volume of 1.7% Nacl, the suspension was centrifuged at 15,000 rpm (4℃) for 60 minutes, and this supernatant is the disrupted body antigen (DB). Antigen S1, S2 and S3 were obtained from antigen S by precipitation with 30%, 60% and 100% ammonium sulfate respectively, and further purified by Sephadex G-100 gel filtration. Using double diffusion, rocket immunoelectrophoresis and polyacrylamide gel electrophoresis, it appears that antigen DB is superior to antigen S in its sensitivity, but it lacks the specific soluble component. The preparation of antigen S is rather simple. S1 contains both the specific soluble component and the component identical with antigen DB. Therefore, S1 is recommended to be further purified for experimental purposes.