In this investigation, the authors examined the effect of attributional processes concerning medication taking on return of fear following exposure-based treatment. Participants (87% undergraduate students and 13% community volunteers) displaying marked claustrophobic fear (N = 95) were randomly allocated to a waitlist condition, a psychological placebo condition, a 1-session exposure-based treatment, or the same exposure treatment given in conjunction with an inactive pill. Attributions concerning medication taking were manipulated by further randomly assigning participants in the exposure-based treatment plus pill condition to 1 of 3 instructional sets immediately following treatment completion and posttreatment assessment: (1) The pill was described as a sedating herb that likely made exposure treatment easier; (2) the pill was described as a stimulating herb that likely made exposure treatment more difficult; or (3) the pill was described as a placebo that had no effect on exposure treatment. Return of fear rates for the 3 conditions were 39%, 0%, and 0%, respectively. Moreover, the deleterious effects of the sedation instructions were mediated by reduced self-efficacy. These findings highlight the importance of assessing patient attributions regarding the improvements achieved with combined exposure-based and pharmacological treatments for anxiety disorders.