The proposed study is a randomized, controlled trial that will assess whether two group interventions for PTSD - Mindfulness-Based Stress Reduction (MBSR) and Cognitive Processing Therapy-Cognitive only (CPT-C) result in similar improvements in PTSD symptoms and health-related quality of life (QOL). One hundred fifty-two Veterans with PTSD will be randomized to MBSR (n = 76) or CPT-C (n = 76). Comprehensive assessments will take place post-treatment and 3 months later.