SUMMARYExisting research demonstrates that nursing homes are the modern mental institutions for the elderly in the United States, but that training of staff and physicians, processes of care, and the recognition and treatment of mental disorders lag behind the current state of scientific knowledge. The prevalence of diagnosable psychiatric disorders has been estimated to be 80% or higher. The most common of these disorders are the dementias, primarily Alzheimer's or vascular, that can be uncomplicated or complicated by the presence of hallucinations, delusions, depression or behavioral symptoms. Other common disorders include depression and delirium. Problems currently under investigation include the effectiveness of special care units for patients with dementia, the characterization and treatment of the non-cognitive, psychiatric symptoms of dementia, including consideration of the appropriate use of psychotropic medications, and the recognition, diagnosis, and treatment of depression. Although there is a clear need for more research, the available data already demonstrate the need for augmented psychiatric input into nursing home care.