The recent development of valid and reliable assessment tools to monitor agitation, sedation, analgesia, and delirium in the ICU represents an essential first step in the provision of patient comfort and the development of preferred treatment strategies. To make the ICU a more humane healing environment, these assessment tools must be used as part of a comprehensive evaluation of interventional and preventive treatments, pharmacologic and nonpharmacologic. In the spirit of the JCAHO, it may be time to add the evaluation of sedation, agitation, and delirium to that of pain assessment, making all aspects of patient comfort the fifth vital sign for the critically ill.