Psychotherapy integration has focused primarily on the underlying commonalities of current systems of treatment. Nevertheless, the process of psychotherapy demands that therapists have an understanding of the underlying psychopathology that is the target for change. Indeed, information regarding the nature of the targeted disorder must inform the process of treatment selection. This paper focuses upon basic psychopathology and treatment outcome data relevant to one anxiety disorder—panic disorder with agoraphobia (PDA). In particular, the importance of targeting the two defining features of this disorder (i.e., panic attacks and agoraphobic avoidance) is emphasized. Moreover, the central role of interoceptive exposure and incorporation of interpersonal systems in providing maximally effective treatment for PDA is reviewed. Lastly, the comprehensive treatment package that has evolved from the research evidence available to date is detailed.