Sleep is important for multiple aspects of heath including immune function, cognitive function, and respiratory function. Animal studies have demonstrated that sleep is important for the removal of waste products from the brain. There is growing interest in the importance of sleep in critically ill patients and sleep problems post-ICU discharge. This meet the professor session will review the importance of sleep in critical illness and sleep problems post-critical illness. The postulated mechanisms between sleep, circadian disruption and delirium will be reviewed. Finally, practical algorithms for sleep improvement in critically ill patients will be presented.