Interest in and the quantity of publications on delirium in critically ill patients have grown increasingly over the last decade. Critically ill patients have traditionally been sedated to facilitate mechanical ventilation. This practice impeded the recognition of delirium in the critically ill patients, and consequently the disorder was underdiagnosed. Delirium in the critically ill patients is associated with increased morbidity and mortality. Less sedation, guided by protocols with daily wake up trials, and validated delirium scoring systems, have improved the opportunities to diagnose and monitor delirium in the critically ill patients.