We investigated the association of 15 exposures, 10 stressors, and 18 life events with illness symptoms reported by 978 veterans who believe they suffer from Gulf War-related illnesses. A mail survey was completed by veterans (60% response rate) from the Gulf War Health Registry. Variables most associated with high symptom group membership were reported chemical/biologic warfare (CBW), concerns with infection and faulty equipment, feelings of mistrust in the military, and disability leading to work stoppage within 2 years after the war. These data suggest that belief in CBW exposure, and the experience of war stress and serious negative life events after the war, are important concomitants of Gulf War illness. Models seeking to explain Gulf War symptoms need to incorporate a range of exposure and psychosocial factors to fully account for important influences.