The relationship of the NEO-PI to personality disorders was evaluated in a clinical population. Eighty subjects with post-traumatic stress disorder (PTSD) were given this measure, along with the MCMI-II and PTSD and combat scales. Two questions were addressed: (1) What is the relationship of NEO-PI domains and facets to personality disorders?; and (2) What is this scale's relationship to PTSD problems? Results support previous studies that employed a clinical population, but with lower correlation coefficients. For the most part, then, the NEO-PI domains and facets correlated in expected ways with the MCMI-II. On PTSD measures, N accounted for the majority of the variance, but other domains were entered when independent regression equations were calculated to account for different personality disorders.