Clinicians commonly sedate critically ill patients. Sedatives should be administered to achieve predetermined end points. Most currently available scales used to assess sedation are inadequate because they focus on a single domain, such as consciousness. The development of the American Association of Critical-Care Nurses' Sedation Assessment Scale is described. This new scale consists of 5 domains: consciousness, agitation, anxiety, sleep, and patient-ventilator synchrony. A major advantage of the scale is that its domains parallel common goals of sedation therapy for critically ill patients. The proposed measurements for each domain are based on a comprehensive evaluation of the science and expert recommendations. Before the scale is widely used, clinical testing is required to determine its validity and reliability in a variety of critically ill patients and care situations.