Objective   To observe the effects of chemical compounds exposure and hyperthermal environment to pregnant rats on the hippocampus neuronal morphology and neurobehavioral development of their offsprings.    Methods   Pregnant rats were divided into 4 groups randomly: the control group; chemical compounds exposure group

chemical compounds combined hyperthermal exposure group and hyperthermal group. The control group was living in normal condition; the chemical compounds exposure group in a cabin with benzene (20.26±0.80) mg/m

3

toluene (39.66±4.23) mg/m

3

dimethylbenzene (42.40±2.85) mg/m

3

and

formaldehyde (23.13±1.30) mg/m

3

; the hyperthermal group was kept in an atmosphere of 38.5 ℃; and the combined group was exposed to the chemical compounds and high temperature at the same time. All animals were treated respectively 2 h per day for 10 d since their pregnancy. Their offspring were lived in normal condition. The development of brain and changes of hippocampus neuronal morphology were observed just or 1 month after born. The primary reflex activity of new-born rats was also examined.    Results   There was no abnormality in the brain of new born rats from 4 groups. In the chemical compounds exposure and the combined exposure groups

the number of degeneration and necrosis neurons in CA1 region of hippocampus were significantly more than those in control and hyperthermal groups (P0.01). A month after born

the number of CA1 neurons were lesser than those in control and hyperthermal groups (P0.01). The time of early period reflex appearance in chemical compounds exposed group

chemical compounds combined hyperthermal exposed group and hyperthermal group were significantly longer than that in control group.    Conclusion   Chemical compounds exposure can induce the degeneration and necrosis of hippocampus neurons. Chemical compounds combined hyperthermal exposure does not aggravate the damage to hippocampus neurons

however hyperthermal environment prolongs the time of early normal period reflex appearance.