It is hypothesized that changes in these potential mechanisms will mediate treatment outcome. The proposed study is a four-treatment condition by three-evaluation period (pre-treatment, post-treatment, and 6-month follow-up) repeated measures factorial design with multiple dependent measures. Participants will be 136 patients with co-morbid chronic pain and PTSD receiving care in the VA Boston Healthcare System. Participants in the active treatment conditions will complete 11 weekly outpatient therapy sessions. A clinical psychologist with specialized training in providing both PTSD and chronic pain treatment protocols will conduct therapy in an individual format, 90 minutes in duration. Participants assigned to the TAU condition will not receive treatment beyond that provided by their primary care provider and other healthcare providers. The Cognitive Behavioral Therapy-PAIN condition will follow an adaptation of a manualized treatment protocol used by Kerns and colleagues that emphasizes identifying and modifying maladaptive thoughts and behaviors related to the experience of chronic pain. Participants in the Cognitive Processing Therapy - PTSD condition will receive a manualized treatment protocol that includes several empirically supported techniques including cognitive restructuring, exposure therapy, and skills training. Participants in the Cognitive Behavioral Therapy - Integrated condition will receive an integrated treatment for comorbid pain and PTSD including components of the pain and PTSD treatments described above.