The timing of events often provides the best clues to the cause of the delirium. Alteration in consciousness is the sine qua non of delirium and is best measured by testing attention. The Glasgow Coma Scale, as modified for the Acute Physiology and Chronic Health Evaluation (APACHE) III study, formally rates consciousness. The Folstein Mini-Mental State Examination (MMSE) is a helpful tool that tests orientation, attention, memory, language, comprehension, and construction. The primary, definitive treatment of delirium is reversal of its underlying cause(s), while dopamine blockade is adjunctive. As a disturbance of consciousness with cognitive, affective, and behavioral manifestations, delirium, put simply, is acute brain failure. Use of dopamine antagonists is adjunctive; haloperidol remains the treatment of choice for fulminant delirium with agitation. Resolution of the delirious state often lags behind reversal of the causative medical or surgical problem.