Recently, health problems caused by environmental chemical substances present in daily life have been increasing, particularly developmental toxicities, the effects of which often become apparent only after a long developmental period. It is difficult to determine adverse transgenerational effects. Therefore, we must recognize important indices to measure neurobehavioral and developmental effects. The assessment of such effects indices, is difficult and few neurobehavioral data are available compared to teratological data. Thus, through studies using laboratory animals, analyses of the mechanisms, exposure periods, doses and neurobehavioral effects are necessary. We have reviewed studies of the volatile monomer of the organic solvent styrene with regard to reproductive and developmental toxicities in laboratory animals. The styrene monomer crosses through the placenta; however, fetal excretion is less than maternal excretion. Therefore, it seems that a dose of styrene that does not affect the mother may be toxic for the fetus. We reported that exposure to low-dose styrene results in physical and neurobehavioral developmental delays, as well as decreases in enzyme activity and neurotransmitter secretion level. To prevent neurobehavioral toxicity, we need further studies to obtain precise data on chemical-biological interactions developmental toxicity and dose-response relationships. A key step towards effective prevention can also be obtained from studies in which animals are continuously exposed to chemicals for one or more generations. Thereafter, we must extrapolate developmental toxicity data from animals to humans. In this paper, we provide the information on developmental toxicity.