Overestimating personal protection afforded by participation in a preventive trial, e.g. harboring a “preventive misconception” (PM), raises theoretical ethical concerns about the adequacy of the informed consent process, behavioral disinhibition, and adherence to prevention interventions. Data from the CAPRISA 004 1 % tenofovir gel trial were utilized to empirically evaluate these concerns. We found it necessary to re-think the current definition of PM during evaluation to distinguish between true misconception and reasonable inferences of protection based on increased access to evidence-based prevention interventions and/or clinical care. There was a significant association between PM and decreased condom use (p < 0.0001) and between PM and likelihood to present with an STI symptom (p = 0.023). There was, however, limited evidence in support of PM representing a lack of meaningful informed consent, or to suggest that it impacts adherence. Moreover, considering current insufficiencies in female-initiated HIV prevention interventions, PM is perhaps of limited concern in microbicide trials.