The cognitive model of panic (Clark, 1988) suggests that panic attacks result from the catastrophic misinterpretation of bodily sensations rather than the sensations themselves. Anxiety sensitivity (AS) is fear of anxious bodily sensations (Reiss, 1991) and has implications in panic development, maintenance, and severity. Although previous work has demonstrated that AS amplifies symptoms in response to provocations, few have analyzed the role of AS in the relationship between panic symptoms and panic disorder severity. The purpose of this investigation was to determine if AS, a cognitive risk for panic, has an indirect effect on the association between self-reported panic symptoms and panic severity, both self-reported and clinicianassessed, among 67 treatment-seeking individuals with a primary diagnosis of panic disorder with or without agoraphobia. Data were analyzed using the bootstrapped conditional process indirect effects model. Results indicated that the overall total mediational effect on Panic Disorder Severity Scale (PDSS) was significant with evidence of partial mediation. The direct effect of Beck Anxiety Inventory (BAI) on PDSS remained significant although there was also a significant indirect effect of BAI via AS. Results showed a similar relationship when Clinician Severity Rating was the outcome. Moderation analyses were not significant. Therefore, AS was a significant partial mediator of the relationship between symptom intensity and panic severity, whether clinician-rated or self-reported. This investigation provides support for the importance of AS in panic, highlighting its importance but suggesting that it is not sufficient to explain panic disorder.Keywords: panic disorder; anxiety sensitivity; mediation; anxietyPanic disorder presents a large disease burden with a 2.8% 12-month prevalence and 4.7% lifetime prevalence; furthermore, when expanded to include all individuals that report panic attacks, the prevalence rates jump to 11.2% 12-month prevalence and 28.3% lifetime (Kessler et al., 2006). In the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013), criteria for a panic attack require an individual to endorse at least four symptoms in a discrete period. Whether situationally bound, situationally predisposed, or uncued, the sudden experience of fearful symptoms is the hallmark of panic.Small to moderate associations between most symptoms and the degree of demonstrated agoraphobic avoidance suggest that there is a relationship between symptom intensity and severity (Berle, Starcevic, Milicevic, Hannan, & Moses, 2010). Combined with the finding that panic disorder with agoraphobia tends to be associated with greater frequency and severity of panic attack symptoms than panic disorder without agoraphobia (Starcevic, Kellner, Uhlenhuth, & Pathak, 1993) and that individuals that frequently exhibit agoraphobic avoidance tend to exhibit all panic symptoms (except for paresthesia) more frequently than those that infrequently avoid (de Jong & Bouman, 1995), there is an association between panic symptoms and severity that may exist above and beyond what one would predict using other relevant phenomenology. Telch, Schmidt, Jaimez, Jacquin, and Harrington (1995) found that the intensity of anxiety symptoms was a better predictor of anxious avoidance than panic attack frequency and that anxiety symptoms and agoraphobic avoidance were better predictors of impairment than panic severity. In addition, the Beck Anxiety Inventory (BAI), which may be a measure of panic symptoms rather than general anxiety symptoms (Cox, Cohen, Direnfeld, & Swinson, 1996), demonstrates a strong correlation with the self-report version of the Panic Disorder Severity Scale (PDSS; Shear et al., 2001), further reinforcing the strength of the association between panic symptoms and severity.In the cognitive model of panic (Clark, 1988), panic attacks result from the catastrophic misinterpretation of certain anxious bodily sensations and the perception of these as more dangerous than they truly are. …