Cognitive Processing Therapy CPT is identified as one of the most effective treatments for posttraumatic stress disorder PTSD in a wide range of trauma populations. This study will test the efficacy of massed intensive outpatient CPT compared to standard CPT delivery. A sample of 140 active duty service members will be assigned randomly to receive either Massed CPT MCPT or standard CPT. MCPT will be delivered in an intensive outpatient setting 12 sessions in 5 days composed of both group and individual sessions. By contrast, standard delivery of CPT consists of 12 sessions over 6 weeks and involves only individual sessions. Participants will be assessed before and after treatment, and several times up to four months after treatment completion to determine if MCPT is as efficacious as standard CPT and to examine predictors of treatment response in each condition.