The high incidence of reported posttraumatic stress disorder (PTSD) among Vietnam veterans has prompted researchers to search for reliable assessment and treatment procedures for this disorder. Although some encouraging preliminary data on the use of the Minnesota Multiphasic Personality Inventory (MMPI) have been obtained, it is uncertain if this instrument can be confidently used to assess PTSD in Vietnam veterans. Two recent studies have found that MMPI scale 8 (Schizophrenia) and scale 2 (Depression) can differentiate PTSD veterans from non-PTSD veterans. Although the 8-2/2-8 high point pair appears to have some validity for describing the behavioral correlates of PTSD, both PTSD and non-PTSD Vietnam veterans produced the same 8-2 high point pair in both of these studies, differing only in elevation and scatter. In addition, researchers have disagreed on what cut-off scores should be used to differentiate PTSD from non-PTSD veterans. Methodological problems in MMPI research on PTSD range from the questionable validity of profiles used to the significant lack of replicability. Even with the variability among results, the data indicate that PTSD Vietnam veterans do score higher on most MMPI subscales than non-PTSD Vietnam veterans. Consequently, there is a need for more research on the use of the MMPI with Vietnam veterans, especially those suffering from PTSD. (NRB)