Although it is recognized that psychosocial variables influence the expression of psychopathology following trauma exposure, physiological variables have received less attention as potential mediators of psychological outcome in trauma victims. The purpose of this study was to examine the relationship of head injury to psychological outcome in 171 combat veterans seeking compensation for service-connected disabilities for mental disorders attributed to etiologies other than head injury. Veterans underwent structured psychiatric diagnostic interview and completed self-report measures of combat exposure, posttraumatic stress disorder (PTSD), depression, and occurrence of head injury. Comparisons between veterans with and without history of head injury indicated that head injury was associated with more severe depression. Regression analysis suggested that head injury predicted depression, but not PTSD, severity.