In an emergency setting, many neurologic conditions present with psychiatric and behavioral symptoms. These symptoms may either be the first manifestation of the neurologic illness or a later occurrence in the progression of the disease. It is important for clinicians evaluating patients with psychiatric symptoms to identify the signs indicating associated neurologic illness and to have strategies for managing the acute, potentially dangerous, neuropsychiatric manifestations of the disease. This article addresses emergency evaluation and management of depression, anxiety, psychosis, mania, suicide attempts, neuroleptic malignant syndrome and other hypermetabolic and amnestic syndromes, somatoform disorders, aggression, and legal issues, such as capacity to accept or refuse treatment.