Meta-Chlorophenylpiperazine (m-CPP), a serotonin agonist and metabolite of the anti-depressant trazodone, was administered chronically to eight moderate to severely affected Alzheimer patients to determine whether it would produce improvement in behavioral symptoms complicating this illness. In doses up to 80 mg/day for 16 days, m-CPP was well tolerated and resulted in small but significant increases in anergy and depression-related symptoms compared with placebo. The effects of chronic m-CPP in this study contrast with the reported beneficial effects of the parent compound trazodone and selective 5-HT reuptake inhibitors in treating behavioral symptoms in Alzheimer patients.