Research involving military service members has shown a strong relationship between combat experiences and increased risk for posttraumatic stress disorder (PTSD) and other mental health problems. Comparatively little research has examined the relationship between combat experiences, PTSD, aggression, and unethical conduct on the battlefield, although news stories sometimes suggest links between unethical conduct and disorders such as PTSD. This study systematically examined whether unethical conduct is a proxy for aggression and whether specific combat experiences and PTSD are independently associated with unethical behavior. The results of this study indicate that aggression (β = 0.30) and specific combat experiences (particularly, witnessing war atrocities [β = 0.14] and fighting [β = 0.13]) are much more strongly associated with unethical conduct than is PTSD (β = 0.04).