With a sample of 120 Gulf War veterans, the present study investigated the main effects of childhood and lifetime trauma, combat exposure, and coping strategies on posttraumatic stress disorder (PTSD), as well as combat exposure's moderating effects on the other variables' relationships with PTSD. Logistic regression results indicated correct classification of PTSD diagnosis for 88% of the participants, with combat exposure and avoidant coping making significant contributions to this classification. Multiple regression results indicated that lifetime trauma, combat exposure, and avoidant coping were strongly related to PTSD symptoms. Multiple regression results also revealed that combat exposure moderated the strength and direction of PTSD's relationships with childhood trauma and avoidant coping. Study findings have implications for longitudinal investigation of PTSD development and preventive interventions.