In independent medical examinations, unjustified claims of posttraumatic stress disorder (PTSD) are to be expected at an increased rate. In a prospective study, consecutive cases of patients claiming PTSD who underwent independent neuropsychiatric evaluation were analyzed. For 61 adult patients, results of three symptom validity tests (Morel Emotional Numbing Test, Structured Inventory of Malingered Symptomatology, and Word Memory Test) were available. Seventy percent of all claimants showed probable negative response bias in at least one of the three tests, 25% in all three tests. High probability of negative response bias was associated with symptom overreporting and demonstration of cognitive deficits in performance tests. The results indicate that high rates of uncooperativeness must be expected in civil forensic patients with claimed PTSD. A multi-method approach to the assessment of response distortion in PTSD claimants is indicated.