Background: While exposure therapy effectively reduces anxiety associated with specific phobias, not all individuals respond to treatment and some will experience a return of fear after treatment ceases. Aims: This study aimed to test the potential benefit of increasing the intensity of exposure therapy by adding an extra step that challenged uncontrollability (Step 15: allowing a spider to walk freely over one's body) to the standard fear hierarchy. Method: Fifty-one participants who had a severe fear of spiders completed two 60-min exposure sessions 1 week apart in a context that was either the same or different from the baseline and follow-up assessment context. Participants were categorized into groups based on the last hierarchy step they completed during treatment (Step 14 or fewer, or Step 15). Results: Those who completed Step 15 had greater reductions in fear and beliefs about the probability of harm from baseline to post-treatment than those who completed fewer steps. Although completing Step 15 did not prevent fear from returning after a context change, it allowed people to maintain their ability to tolerate their fear, which earlier steps did not. Despite some fear returning after a context change, individuals who completed Step 15 tended to report greater reductions in fear from baseline to the follow-up assessment than participants who completed 14 or fewer steps. Conclusions: Overall, these results suggest that more intensive exposure that directly challenges harm beliefs may lead to greater changes in fear and fear beliefs than less intensive exposure.