Abstract: Panic disorder refers to recurrent, unexpected panic attacks, followed by at least 1 month of persistent concern about their recurrence and their consequences or a significant maladaptive change in behavior consequent to the attacks. Highly comorbid with panic disorder, agoraphobia refers to marked fear or avoidance of specific situations from which escape is perceived to be difficult or in which help may be unavailable in the event of panic-like or other incapacitating or embarrassing symptoms. This chapter focuses on the assessment of panic disorder and agoraphobia in adults. It begins with a review of the nature of the disorders, which is followed by a review of clinical assessment instruments designed for the assessment purposes of (a) diagnosis, (b) case conceptualization and treatment planning, and (c) treatment monitoring and evaluation. Recommendations are included for instruments with the greatest scientific support and for assessing these anxiety disorders in a clinically sensitive manner.