Psychological assessment of anxiety disorders is important in both clinical and research settings. This chapter reviews the various purposes of assessment, discusses issues related to diagnostic assessment, and highlights other areas that are relevant in the evaluation process (e.g., anxiety triggers, avoidance behavior, interference, psychosocial influences, etc.). A variety of assessment methods is discussed, including clinical interviews, behavioral tests, psychophysiological measurement, and behavioral diaries, and the use of multimethod assessment strategies is encouraged. A brief overview of empirically supported assessment measures is also provided.