Drugs with improved potency and specificity are becoming available for the pharmacologic manipulation of serotonin neurons in brain. Both enhancement and impairment of serotoninergic function can now be achieved by drugs acting through different mechanisms. Drugs of this sort are not only valuable tools for exploring functional roles of serotonin neurons but they have real or potential value in the treatment of diseases like mental depression, obesity, myoclonus or other movement disorders, pain, hypertension, and endocrine dysfunction.