Natural products have a long history of being the sources for therapeutic drugs in medicine. Investigations of natural products also have the potential for enhancing our understanding about the pathophysiology and treatment of various disorders. The screening assays described here were conducted on the phytochemical and pharmacological profiles of natural products used to treat psychotic illnesses in Korean traditional medicine, which are eligibly archived in Tongeuibogam, a traditional medicinal book in Korea. Two rounds of radioligand receptor binding assays on natural products demonstrated that many plants show potent selectivity to various receptors, especially monoamine receptors presumed to be involved in mental disorders. Further studies for the pharmacologic activity of active ingredients and in vivo behavioral profiles focusing on the central nervous system (CNS) effects are currently under way with these plant extracts. These investigations may lead to the development of new psychotropic drugs with no serious side effects, a major concern for modern psychopharmacology.