The Minnesota Multiphasic Personality Inventory-2-RF (MMPI-2-RF) validity scales were evaluated to determine accuracy when differentiating honest responding, random responding, genuine posttraumatic stress disorder (PTSD), and feigned PTSD. Undergraduate students (n = 109), screened for PTSD, were randomly assigned to 1 of 4 instructional groups: honest, feign PTSD, half random, and full random. Archival data provided clinical MMPI-2-RF profiles consisting of 31 veterans diagnosed with PTSD. Veterans were diagnosed with PTSD using a structured interview and had passed a structured interview for malingering. Validity scales working as a group had correct classification rates of honest (96.6%), full random (88.9%), genuine PTSD (80.7%), fake PTSD (73.1%), and half random (44.4%). Results were fairly supportive of the scales' ability to discriminate feigning and full random responding from honest responding of normal students as well as veterans with PTSD. However, the RF validity scales do not appear to be as effective in detecting partially random responding.