The effects of MeOH extracts of ninety kinds of medicinal herbs on dopamine content in PC12 cells were investigated. Among them, the MeOH extracts at a concentration of $40;{mu}g/ml$ of Symplocarpus renifolius, Adenocaulon himalaicum and Mosla punctulata decreased $38.5{sim}60.0%$ of dopamine content. Tyrosine hydroxylase, the rate-limiting enzyme of the catecholamine biosynthesis, was inhibited by the treatment of the MeOH extracts of Symplocarpus renifolius, Adenocaulon himalaicum and Mosla punctulata ($19.9{sim}31.3%$ inhibition at $40;{mu}g/ml$). These results suggested that these bioactive herbal medicines exhibited partially an inhibitory effect on dopamine biosynthesis by the reduction of tyrosine hydroxylase activity in PC12 cells.