To improve methods of estimating use of evidence-based psychotherapy for posttraumatic stress disorder in the Veteran's health administration, we evaluated administrative data and note text for patients newly enrolling in six VHA outpatient PTSD clinics in New England during the 2010 fiscal year (n = 1,924). Using natural language processing, we developed machine learning algorithms that mimic human raters in classifying note text. We met our targets for algorithm performance as measured by precision, recall, and F-measure. We found that 6.3 % of our study population received at least one session of evidence-based psychotherapy during the initial 6 months of treatment. Evidence-based psychotherapies appear to be infrequently utilized in VHA outpatient PTSD clinics in New England. Our method could support efforts to improve use of these treatments.