The incremental validity and clinical utility of the recently developed Minnesota Multiphasic Personality Inventory-2 (MMPI-2) Infrequency Posttraumatic Stress Disorder Scale (Fptsd) was examined in relation to the family of MMPI-2 F scales in distinguishing feigned post-traumatic stress disorder (PTSD) from disability claimants with PTSD. Research participants instructed to feign PTSD when completing the MMPI-2 scored significantly higher on the MMPI-2 family of F scales and the Fptsd scale compared with their responses when completing the MMPI-2 under standard instructions and the sample of claimants with PTSD. Although comparable in magnitude, effect sizes derived from mean group differences and hierarchical logistic regressions for the Fptsd scale never exceeded those for F[B], and F[P], F, F[B], and F[P] added incrementally to Fptsd in the prediction of feigned PTSD. These results suggest that the Fptsd scale does not afford any incremental predictive utility for detecting feigned PTSD relative to the complement of the existing family of F scales. (Contains 6 tables, 3 figures and 3 notes.)