The Clinician-Administered PTSD Scale (CAPS) is a structured interview for assessing posttraumatic stress disorder (PTSD) diagnostic status and symptom severity. In the 10 years since it was developed, the CAPS has become a standard criterion measure in the field of traumatic stress and has now been used in more than 200 studies. In this paper, we first trace the history of the CAPS and provide an update on recent developments. Then we review the empirical literature, summarizing and evaluating the findings regarding the psychometric properties of the CAPS. The research evidence indicates that the CAPS has excellent reliability, yielding consistent scores across items, raters, and testing occasions. There is also strong evidence of validity: The CAPS has excellent convergent and discriminant validity, diagnostic utility, and sensitivity to clinical change. Finally, we address several concerns about the CAPS and offer recommendations for optimizing the CAPS for various clinical research applications. Depression and Anxiety 13:132–156, 2001 © 2001 Wiley-Liss, Inc.