I labelled T. gondii parasites were injected via tail vein into 14 day pregnant mouse( Kunming strain). Radioactive tracings of fetal train and pathologic changes were studiet. The results revealed that infection rates in the pregnant mice and in their fetal heads were 30.60% and 71.2% respectively. The ratio of the radioactivity between the fetal heads and the fetal trunks was 1.32-5.95 , being directly proportional to the durations of infection. Autoradiographs of light and electron microscopy indicated that the parasites appeared in the neurogliocytes of the fetal mice as early as 4 8 h post infection, and might be seen in the nucleus 48h after infection with degeneration and rupture of the cells. Numbers of the cranial nerve cells was distinctively reduced at 72h post infection. This study thus provided the experimental pathology evidence for the development of fetal neural malformation and cerebral lesions from T. gondil infected dam mouse. I labelled T. gondii parasites were injected via tail vein into 14 days pregnant mouse (Kunming strain). Radioactive tracings of fetal train and pathologic changes were studiet. The results revealed that infection rates in the pregnant mice and in their fetal heads were 30.60% and 71.2% respectively. The ratio of the radioactivity between the fetal heads and the fetal trunks was 1.32-5.95, being directly proportional to the durations of infection. Autoradiographs of light and electron microscopy indicated that the parasites were present in the neurogliocytes of the fetal mice as early as 4 8 h post infection, and might be seen in the nucleus 48h after infection with degeneration and rupture of the cells. Numbers of the cranial nerve cells was distinctively reduced at 72h post infection. This study thus provides the experimental pathology evidence for the development of fetal neural malformation and cerebral lesions from T. gondil infected dam mouse.