Psychotic symptoms in older individuals may be more common than was previously thought. Most kinds of psychosis that occur in younger people can be seen in older patients. However, there are important clinical differences between early-onset and late-onset psychosis. Conditions in which psychotic symptoms may occur in older adults include chronic illnesses such as dementia, schizophrenia, and delusional disorder, and acute transient disorders such as delirium and substance-induced psychosis. In this article, we focus on psychosis in chronic disorders in older individuals and discuss presentation and treatment of psychosis in patients with early-onset schizophrenia who have lived into old age, late-onset schizophrenia, very late-onset schizophrenia-like psychosis, delusional disorder, and Alzheimer's disease and other dementias.