Abstract: The influence of Toxoplasma gondii infection on the success of mice pregnancy was investigated in this paper. Immunohistochemistry was applied to locate immunocytes in the uterus, and enzyme-linked immunosorbent assay(ELISA) was conducted in order to determine the contents of tumor necrosis factor-α(TNF-α) and interleukin-10 in uterine lysates. All the mice were aborted when the Toxoplasma gondii were incubated intraperitoneously on day 0 or day 6 of pregnancy. A few CD8⁺T lymphocytes were scattered in the endometrium of infected animals, while none cells were seen in the control mice. Large number of F4/80⁺ macrophages were counted in the infected mice. A few were seen in the control group. TNF-α level was significantly higher(76.862±30.354 pg/mg protein) in the infected mice compared with the control animals(P<0.01),indicating a close correlation between pregnancy failure and Toxoplasma infection. IL-10 contents were 19.696±9.811 pg/mg protein in the supernatants of the mice infected with Toxoplasma on day 0, significantly lower than those of control group(48.856±16.518 pg/mg protein,P<0.05). No significant differences of IL-10 contents were observed between the infected mice and controls when infection was carried out on day 6 of pregnancy (P>0.05).