BACKGROUND: Elective surgery can have long-term psychological sequelae, especially for patients who experience intraoperative awareness. However, risk factors, other than awareness, for symptoms of posttraumatic stress disorder (PTSD) after surgery are poorly defined, and practical screening methods have not been applied to a broad population of surgical patients. METHODS: The Psychological Sequelae of Surgery study was a prospective cohort study of patients previously enrolled in the United States and Canada in 3 trials for the prevention of intraoperative awareness. The 68 patients who experienced definite or possible awareness were matched with 418 patients who denied awareness based on age, sex, surgery type, and awareness risk. Participants completed the PTSD Checklist-Specific (PCL-S) and/or a modified Mini-International Neuropsychiatric Interview telephone assessment to identify symptoms of PTSD and symptom complexes consistent with a PTSD diagnosis. We then used structural equation modeling to produce a composite PTSD score and examined potential risk factors. RESULTS: One hundred forty patients were unreachable; of those contacted, 303 (88%) participated a median of 2 years postoperatively. Forty-four of the 219 patients (20.1%) who completed the PCL-S exceeded the civilian screening cutoff score for PTSD symptoms resulting from their surgery (15 of 35 [43%] with awareness and 29 of 184 [16%] without). Nineteen patients (8.7%; 5 of 35 [14%] with awareness and 14 of 184 [7.6%] without) both exceeded the cutoff and endorsed a breadth of symptoms consistent with the Diagnostic and Statistical Manual Fourth Edition diagnosis of PTSD attributable to their surgery. Factors independently associated with PTSD symptoms were poor social support, previous PTSD symptoms, previous mental health treatment, dissociation related to surgery, perceiving that one's life was threatened during surgery, and intraoperative awareness (all P ≤ 0.017). Perioperative dissociation was identified as a potential mediator for perioperative PTSD symptoms. CONCLUSIONS: Events in the perioperative period can precipitate psychological symptoms consistent with subsyndromal and syndromal PTSD. We not only confirmed the high rate of postoperative PTSD in awareness patients but also identified a significant rate in matched nonawareness controls. Screening surgical patients, especially those with potentially mediating risk factors such as intraoperative awareness or perioperative dissociation, for postoperative PTSD symptoms with the PCL-S is practical and could promote early referral, evaluation, and treatment.