Lifetime trauma history was assessed in a health study of active duty United States Army soldiers. Five hundred fifty-five male and 573 female soldiers in the sample were asked whether they had ever experienced 14 different potentially traumatic experiences, including sexual assaults, violent stressors to self, and terrifying events that occurred to others and were secondarily traumatic through exposure by gaining information or as a witness to the event. Most soldiers had experienced multiple traumas, and premilitary exposure to events was much more common than exposure to events after entering the military. Global measures of current psychological distress and physical health symptoms were predicted by the lifetime number of sexual assaults and traumas to self. Social support from military unit leaders moderated the relationship between accumulated exposure to traumas and both health measures, whereas unit cohesion was directly associated with fewer mental health problems.