The purpose of this study was to evaluate the pattern of cognitive change, and in particular the role of negative self-statements, in relation to improvement during an in vivo exposure treatment. Eight panic disordered patients with agoraphobia, of whom 4 were most and 4 were least improved on a composite measure, were exposed to standardized agoraphobic situations. During the exposure, heart rate, self-statements, and subjective anxiety were registered throughout the sessions. Fixed criteria were set for habituation of heart rate and reduction of subjective anxiety within a session. Results showed that the total frequency of negative self-statements at the start, during, as well as at the end of treatment differentiated best between the most and least improved patients. These results suggest that it may be therapeutically wise to continue exposure therapy not only until habituation of anxiety (subjectively and physiologically) is achieved, but also until the frequency of negative self-statements is reduced until zero.