We have developed screening technology to identify environmental chemicals affecting the brain. Environmental chemical was administered into the rat brain at 5 days of age, and spontaneous motor activity was measured at 4-5 weeks of age. Some of phenols and phthalates caused hyperactivities similarly to a neurotoxin, 6-hydroxydopamine [Fig.]. The histological analysis revealed that some phenols, such as bisphenol A, blocked the development of dopaminergic neurons. This technique is expected not only to draft the regulation for chemicals but also to contribute to the creation of better chemical substitutes and new drugs for prevention or treatment of mental disorders.