A questionnaire study was conducted to investigate the psychological adjustment of people who had been aid workers overseas. Nearly fifty percent of the sample of returned aid workers (n = 145) reported that they had experienced psychological difficulties while they were overseas or following their return to Britain. Most had not received any treatment for their difficulties. People who reported psychological problems had, on average, spent longer as aid workers than those who reported no psychological problems. Compared with a group of people preparing for their first term as overseas aid workers (n = 43), returned aid workers had significantly higher mean scores on measures assessing depression, intrusive thoughts, and, among women, avoidance. Aid workers who invalidated their feelings appeared to be especially vulnerable to developing psychological difficulties. When compared with people who did not intend to become aid workers (n = 71), returned aid workers and people preparing to become aid workers were found to perceive the world as a more benevolent and meaningful place. However, a small proportion of returned aid workers expressed views that the world was malevolent and meaningless; such views were related to the development of psychological problems. This finding was discussed with relation to Janoff-Bulman's (1992) theory of shattered assumptions. Implications of the findings were considered, including implications for the selection, preparation and treatment of aid workers.