The accident at the Three Mile Island (TMI) nuclear power station occurred in March 1979. Although the original mishap may not have been as acutely stressful and overwhelming as other cataclysmic events, sources of threat appear to have remained for people living near the damaged reactor. This chapter discusses data obtained from people living near TMI that show that 28 months after the accident, TMI area residents continued to exhibit higher levels of stress than did people in control areas less affected by the disaster. It examines some possible reasons for the persistent stress and considers potential mediators of chronic stress. Self-reported symptoms of stress indicated that TMI area residents who reported lower perceived control reported the most symptoms. They also indicated experiencing the most somatic distress and depression. The residents at TMI do not even know if they were exposed to radiation, yet they have continued to exhibit symptoms of stress for years.