The present study examined the relationship between military service during the Vietnam era and chronic stress among Vietnam combat veterans, noncombat military controls, and nonmilitary age-mates. Psychological, behavioral, and biochemical indices of stress were assessed. Results demonstrated that exposure to combat was not associated with symptoms of chronic stress. However, reported intrusiveness of recalled imagery associated with stressful combat events was an important predictor of long-term symptoms of stress irrespective of combat exposure. In addition, the interaction of combat exposure and intrusive thinking was significantly related to symptoms of chronic stress. These data suggest that intrusive thinking may reflect an important individual difference variable that could help predict long-term responding to stressors.