['This study examined the degree to which combat-related guilt mediated the relations between exposure to combat-related abusive violence and both Posttraumatic Stress Disorder (PTSD) and Major Depressive Disorder (MDD) in Vietnam Veterans.', 'Secondary analyses were conducted on data collected from 1,323 male Vietnam Veterans as part of a larger, multisite study.', 'Results revealed that combat-related guilt partially mediated the association between exposure to combat-related abusive violence and PTSD, but completely mediated the association with MDD, with overall combat exposure held constant in the model. Follow-up analyses showed that, when comparing those participants who actually participated in combat-related abusive violence with those who only observed it, combat-related guilt completely mediated the association between participation in abusive violence and both PTSD and MDD. Moreover, when comparing those participants who observed combat-related abusive violence with those who had no exposure at all to it, combat-related guilt completely mediated the association between observation of combat-related abusive violence and MDD, but only partially mediated the association with PTSD.'] Does combat-related guilt mediate the relations between exposure to combat-related abusive violence and psychiatric diagnoses?