Psychotic symptoms have become increasingly common in patients with idiopathic Parkinson's disease and other parkinsonian syndromes. This increased prevalence of psychoses is in part a reflection of the greater longevity of people with Parkinson's disease and, to a certain extent, is a consequence of our success in treating the motor symptoms of these syndromes. The psychotic symptoms associated with Parkinson's disease can be as varied as the motor symptoms. They stem from interactions between the underlying neuropathologies of the syndromes and the adverse effects associated with chronic antiparkinsonian drug administration. In patients with advanced Parkinson's disease, there is also a high prevalence of affective comorbidity. This increase in affective symptoms and the relatively high incidence of cognitive and affective side effects of the antiparkinsonian medications contribute to the increase in psychoses observed in these older patients. The most significant risk factors for developing psychosis in Parkinson's disease are (1) coexistence of dementia, (2) protracted sleep disturbances, and (3) nighttime use of long-acting dopaminomimetics. This article reviews the phenomenology, pathophysiology, and treatment of psychosis associated with parkinsonism and discusses how atypical antipsychotic medications have revolutionized the management of the symptoms and improved the quality of life of those affected.