Previous research has shown that psychological treatments, particularly those employing cognitive techniques, are particularly effective in the treatment of irritable bowel syndrome (IBS). It is presumed that these psychological interventions are effective at ameliorating the IBS by treating an underlying psychological disorder (often an anxiety disorder), which may be contributing to the autonomic reactivity. This case study examined the change in the physical symptoms of IBS for a patient seeking treatment for rape-related PTSD with comorbid conditions of major depression and panic. At posttreatment, the patient no longer met criteria for PTSD, major depression, or panic. In addition, her primary symptom of IBS, diarrhea frequency, was significantly improved. These findings were maintained at 3 and 9 months posttreatment. Implications for the assessment and treatment of IBS patients with PTSD are discussed.