This study examined responses to loud tones before and after cognitive–behavioral treatment for posttraumatic stress disorder (PTSD). Seventy-four women in a PTSD treatment outcome study for rape-related (n = 54) or physical assault-related PTSD (n = 20) were assessed in an auditory loud tone paradigm. Assessments were conducted before and after a 6-week period of cognitive–behavioral therapy. Physiologic responses to loud tones included heart rate (HR), skin conductance (SC), and eye-blink electromyogram (EMG). Groups were formed based upon treatment outcome and included a treatment responder group (no PTSD at posttreatment) and a nonresponder group (PTSD-positive at posttreatment). Treatment was successful for 53 of 74 women (72%) and unsuccessful for 21 women (28%). Responders and nonresponders were not significantly different from each other at pretreatment on the main outcome variables. Treatment responders showed a significant reduction in loud tone-related EMG, HR, and SC responses from pre- to posttreatment (partial η2 = .24, .31, and .36, respectively; all p < .001) and the EMG and HR responses were significantly smaller than nonresponders at posttreatment (partial η2 = .11, p = .004 and .19, p < .001, respectively). Successful cognitive–behavioral treatment of PTSD is associated with a quantifiable reduction in physiological responding to loud tones.