Assessments of mental health (GHQ-28) were performed on a Swedish battalion serving in Bosnia at 4 times: before deployment, immediately after deployment, 6 months after deployment, and 1 year after deployment. Complete responses were obtained from 316 participants (61% response rate). No significant change of mental health over time was noted. Individuals having experienced traumatic events in Bosnia, as well as stressful life events postdeployment, reported the poorest mental health. Logistic regression analysis showed that postdeployment stressors made the strongest contribution to registering a poor mental health score after one year.