Participants in this study will begin a psychotropic medication washout period for up to 3 days at study start. Participants will then be randomly assigned to receive either citalopram or risperidone for up to 12 weeks. Limited doses of the sedative lorazepam may be administered as needed throughout the study. During the first 2 weeks of the study, participants will be admitted to a hospital to have their dementia-related behavioral disturbances stabilized. Following hospital discharge, participants will move to a long-term care facility or a residential home and will continue medication treatment for up to 10 weeks. Side effects and improvements in behavioral status will be assessed every week until Week 6 and every 2 weeks thereafter. Experimental laboratory measures will be collected at study start, Week 1, Week 2, and every 2 weeks thereafter until Week 12. Upon study completion, patients may continue to receive citalopram or risperidone under the supervision of their current physicians. Three months after study completion, participants may be contacted for a follow-up report of their psychiatric and medical status.