Many patients evince significant post-traumatic stress disorder (PTSD) symptoms after a dose of an evidence-based treatment (EBT) for PTSD. Little research systematically addresses if individual PTSD symptoms are more or less resistant to change through an EBT for PTSD or have greater or lesser post-treatment severity levels. Two studies within VA medical centers provided data. Study 1 (n = 81) was drawn from a randomized clinical trial of Prolonged Exposure (PE), an EBT for PTSD. Study 2 (n = 225) was drawn from two PTSD specialty clinics employing PE. Symptoms were assessed pre- and post-treatments via semi-structured clinician interview (Study 1) and patient self-report (Studies 1 and 2). Most individual symptoms reduced about the same amount through the course of treatment except for avoidance, which showed greater reductions. High heterogeneity in post-treatment symptom severity was found with troubled sleep and hypervigilance displaying above average levels, and traumatic amnesia, foreshortened future, and flashbacks displaying below average levels. Method of symptom measurement had a modest impact on results, as semi-structured clinical interview results were moderately more differentiated than self-report measures. Results were generally consistent between an efficacy (i.e., extremely high, potentially artificial methodological control) and effectiveness (i.e., relatively more real world) context. Primary limitation is analysis of single items on semi-structured clinician interview and patient self-report scale when psychometric validation studies did not interpret measures this way. Moreover, DSM-IV criteria for PTSD were assessed. EBT augmentation and new treatment development should focus on further reducing both PTSD symptoms in general and on the specific symptoms of troubled sleep and hypervigilance, which persist to a greater degree. (PsycInfo Database Record (c) 2023 APA, all rights reserved).