In the present study, we explored factors related to successful treatment outcome in a sample of participants with fear of spiders. We specifically examined the relationship of general memory, memory for the phobic stimulus, memory for anxious responses, and perceived self-efficacy to treatment outcome. Forty-eight participants who were afraid of spiders participated in two sessions of in vivo exposure therapy. On day 1, participants completed measures of general memory, memory for the phobic stimulus, recall of anxiety level during exposure tasks, and self-efficacy during exposure tasks. At post-treatment, better memory for anxious responses, but not memory for the phobic stimulus, was related to lower anticipatory and actual anxiety. Greater self-efficacy, on the other hand, was related to better behavioral performance.