Acute brain dysfunction, usually manifested as delirium, occurs in up to 80% of critically ill patients. Delirium increases costs of hospitalizations and affects short-term outcomes such as duration of mechanical ventilation, intensive care unit (ICU) length of stay, and the hospital length of stay. Long-term consequences-cognitive impairment and increased risk of death-can be devastating. For adequate recognition and management it is imperative to implement a successful delirium monitoring and assessment strategy. A liberation and animation strategy can reduce both the incidence and the duration of delirium. Liberation aims to reduce the harmful effects of sedative exposure through use of target-based sedation protocols, spontaneous awakening trials, and proper choice of sedative as well as liberation from the ventilator and the ICU. Animation refers to early mobilization, which reduces delirium and improves neurocognitive outcomes. Delirium is a serious problem with important consequences and can be prevented or improved using the information that we have learned in the last decade.