Failure of general anesthesia to render a patient insensate, termed "awareness," is estimated to affect between 40,000 and 140,000 patients in the US each year. This study investigated the occurrence of post-traumatic stress disorder (PTSD) in subjects who reported a past episode of intraoperative awareness. We inquired about intraoperative and postoperative experiences and studied the relationship between various surgical experiences and currently meeting the diagnosis of PTSD. Sixteen postawareness subjects and 10 postgeneral anesthesia controls completed the Clinician Administered PTSD Scale (CAPS), a standardized clinical rating scale for PTSD, and a questionnaire about peri-operative experiences. Nine of 16 subjects (56.3%), a mean of 17.9 postoperative years, and no controls met diagnostic criteria for current PTSD (X(2)= 8.6, df = 1, P<.01). Common intraoperative experiences included an inability to communicate, helplessness, terror, and pain. Postawareness patients had significant postoperative distress related to feeling unable to communicate, unsafe, terrified, abandoned and betrayed. Perioperative dissociative experiences predicted having current PTSD. Being conscious during surgery is a traumatic event that may result in developing chronic PTSD. Further studies should include prospective designs of prevalence and long-term psychological, social, and overall health effects, and ways of preventing and treating awareness-induced PTSD.