Abstract: Objective To evaluate the reproductive toxicity of different degree Toxoplasma gondii infection on BALB/c mice.Methods Fertilized BAL B/c mice were divided into 5 groups randomly(10 in each group).On the 8th day of pergnancy,the negative control group was given aseptic phosphate buffer solution;the low,mode rate,and high dose expermient group were exposed to 50,100,200 Toxoplasma gondii tachyzoite ;sthe positive control group was exposed to cyclophosphamide at 8 th and 10th day of pregnancy.All the treamtents were administered with intrape ritoneal in jection.On the 18 th day of preg nancy,the conditions of preg nant mice and foetus were examined.Results Contrast with the negative control group,positive control group showed significant higher rates of foetusabsorption(19.6%),still birth(23.6%),abnormal embryo(4.6%),and teratism(31.4%)(P<0.05 for all).In mode rate dose group,the rate of foetus absorption,still birth,and abnormal embryo was 15.7%,8.2%,5.8% and those of the high dose group was 28.9%,12.5%,and 15.1%,respectively,with significant differences compared with those of the negative control group(P<0.05 for all).The teratism rate was obviously higher in high dose group than in the control(27.3% vs 0,P<0.01).Conclusion Infection with 100 or 200 RH Toxoplasma tachyzoite in the middle of gestational period induce reproductive toxicity in BALB/c mice.