Posttraumatic stress disorder (PTSD) is one of the fastest growing compensated medical conditions. The present study compared usual disability examiner practices for PTSD with a standardized assessment that incorporates evidence-based assessments. The design was a multicenter, cluster randomized, parallel-group study involving 33 clinical examiners and 384 veterans at 6 Veterans Affairs medical centers. The standardized group incorporated the Clinician Administered PTSD Scale and the World Health Organization Disability Assessment Schedule-II into their assessment interview. The main outcome measures were completeness and accuracy of PTSD diagnosis and completeness of functional assessment. The standardized assessments were 85% complete for diagnosis compared to 30% for nonstandardized assessments (p < .001), and, for functional impairment, 76% versus 3% (p < .001). The findings demonstrate that the quality of PTSD disability examination would be improved by using evidence-based assessment.