Although there are several treatment options available for posttraumatic stress disorder (PTSD) none of them have a 100% success rate. Approximately half of the individuals who complete CBT will continue to show symptoms of the disorder, and little progress has been made in discovering biological predictors of treatment response in the disorder. Finding such biological predictors would be useful in helping select a treatment that is best for individual patients, thereby increasing the number of individuals who no longer exhibit PTSD symptoms. Using functional magnetic resonance imaging (fMRI), we measured brain activation in 14 participants who passively viewed emotional facial expressions before receiving eight sessions of prolonged exposure therapy (PE). Response to treatment was measured using clinician-administered scales---the Short PTSD Rated Interview (SPRINT) and the Clinical Global Improvement (CGI-I) scale. We conducted correlations in order to assess the relationship between participants' pre-treatment brain activation and their improvement scores on each of these scales. Overall, our results showed that greater pre-treatment activation in the rostral anterior cingulate cortex (rACC) and lower pre-treatment activation in the amygdala led to better responses to treatment. These results suggest that measuring brain activation may be a useful tool to use in the future to predict treatment response.