Inclusion Criteria:

• Meets DSM-IV criteria for diagnosis of dementia of the Alzheimer's type (AD), Vascular dementia (VD), mixed (AD and VD) or dementia NOS (Not Otherwise Specified)
• Presents with psychosis or behavioral problems severe enough to endanger the patient's health, well-being or safety, as evidenced by a score of at least 3 (moderate) on one of the Neurobehavioral Rating Scale (NBRS) agitation items (8,11,14) or psychosis items (16,18,20) and are not secondary to physical illness nor amenable to environmental optimization
• Able to participate in study evaluations and ingest oral medication
• Has next of kin or a guardian available to consent to patient's participation.

Exclusion Criteria:

• Has an unstable medical illness including significant cardiac (specifically bradycardia with ventricular rate below 50), renal, hepatic, or neurological illness (especially Parkinson's disease) other than dementia
• Meets DSM-IV criteria for Delirium upon admission to Western Psychiatric Institute and Clinic
• Has been medicated within 4 weeks of protocol admission with fluoxetine or 2 weeks with a monoamine oxidase inhibitor (patients will undergo a monitored psychotropic drug washout prior to entering the protocol)
• Is currently being treated with cognitive enhancing drugs (Tacrine or Aricept) or any experimental drug
• Has a concurrent diagnosis of schizophrenia, bipolar disorder, or major depression
• Has preexisting orthostatic hypotension (with > 20 mmHg change from sitting to standing pressure)