Resting immune [WBC and differential cell counts, lymphocyte phenotyping (CD2, CD4, CD8, CD16, CD20, and CD56), and NK activity] and endocrine (cortisol, prolactin, growth hormone, and DHEA-SO4) parameters were measured in 10 male, Vietnam combat veterans diagnosed with long-term post-traumatic stress disorder (PTSD) and 9 control Vietnam combat veterans without a PTSD diagnosis but with a comparable history of alcohol abuse. Subjects completed a battery of psychological questionnaires. We report on preliminary observations of the relationship between PTSD and physiological and psychological parameters. With some important exceptions. PTSD patients. did not differ from the age-matched control group with regard to hormone levels or lymphocyte phenotypes. However, NK activity was higher in the PTSD population than in the controls. Beck, Mississippi, and Combat Exposure scores were significantly elevated in the PTSD population. in contrast to previous observations in depressed populations, depression (indicated by elevated Beck scores), comorbid with PTSD, was associated with increased natural cytotoxicity. (C) 1998 Academic Press.