The MMPI-PTSD scale is the only psychometric measure that has been cross-validated on Vietnam veterans for the determination of PTSD. Despite this, there may be problems with this scale related to symptom exaggeration. Three groups of Vietnam inpatients (N = 75) were defined carefully by both clinical and actuarial methods--PTSD combat, Non-PTSD combat, and Non-combat. This study applied symptom exaggeration methods based on the MMPI obvious/subtle items and on the F scale to these groups. Results show that all the items of this scale are either obvious or neutral, that a carefully distinguished PTSD group differentially responds to these obvious and neutral items relative to other inpatient Vietnam groups, and that the F scale is exaggerated by the PTSD group. In addition, a separate analysis on an independent sample of 50 combat and 50 non-combat Vietnam veterans showed that the combat group endorsed the obvious items on selected scales by 20 T score points at higher rates than other groups. Caution in the use of the MMPI-PTSD scale is discussed.