Background: Anxiety activates the sympathetic nervous system and hypothalamic-pituitary-adrenal axis and may increase morbidity and mortality in vulnerable critical care patients. Despite the adverse effects of anxiety, little is known about critical care nurses' practices for assessing anxiety. Objective: To determine the importance that critical care nurses place on evaluating anxiety and to describe clinical indicators used to assess anxiety. Methods: Twenty-five hundred members of the American Association of Critical-Care Nurses received the Critical Care Nurse Anxiety Identification and Management Survey and were asked to rate the importance of anxiety assessment, to rate the importance of 61 anxiety indicators, and to select and rank the 5 most important anxiety indicators. Results: Seven hundred eighty-three completed surveys (31.6%) were returned by female (92.0%), white (88.6%) staff nurses (74.2%) who practiced critical care nursing 32.5 hours (SD, 12.3 hours) weekly. Nearly three quarters (71.3%) of respondents thought that anxiety assessment is very important. Only 2 indicators, agitation and patients' verbalization of anxiety, were rated as very important to anxiety assessment. Thirty-nine indicators rated as important primarily included measurable physiological changes and observable behaviors. The top 5 anxiety indicators were agitation, increased blood pressure, increased heart rate, patients' verbalization of anxiety, and restlessness. Conclusion: Important indicators of anxiety included observable behaviors and measurable physiological changes. Reliance on these criteria may produce an inaccurate and incomplete anxiety evaluation in vulnerable patients and lead to poorer outcomes. A comprehensive, systematic anxiety assessment tool for valid and reproducible evaluation of patients' anxiety is needed.